Me and my friend have played many games were we might be doing good in the earlygame but eventually get pushed back to our base andare on the defense until we lose or surender. My question is if it is possible to win a game when all your turrets are down and you are at your base. Please give us some tips. thanks

No you can't just surrender lulz
OK just kidding well if your inhibitors aren't destroyed it may be possible because winning players often get over confident and lack the teamwork needed for the last heavy push. So if you are more organized you could push back. But if all your inhibitors are down and you are pushed to the Nexus towers well... I've never seen someone push back and win in that situation :\

It's pretty tough, if you have Inhibs down it is very challenging to push out as the super creeps can just come in and clean off your nexus. If your Inhibs respawn and you are able to teamwipe them you can turn around and win. It is very challenging and I have only done it twice out of about 50-60 games that went this way. You will begin to know when you have lost, sometimes there is no question that you will not beable to come back, but don't always count it as impossible.
Of course, if u have a decent, Yi, Shaco, TF, Twitch, you can backdoor them while the rest of you defend in base.

with just all turrets down, it's quite possible. on an ace, your team can take down at least one of their inhibitors, if not 2, before they rez.

i've won many times with one inhibitor disadvantage, where we all pushed the weak lane and killed a few champions on the way, then took their inhibitors.

two or more inhibitor disadvantage is very hard to recover from, i'd say. all they have to do is play cautiously and the super minions will wear your team down.

The best way to fix your problem is to not be in the situation to begin with (fixing midgame play is a lot easier than coming from behind lategame).

Around the time everyone hits level 6, the most important part of the game becomes winning teamfights. Make sure you have an advantage in manpower before you initiate and if at all possible, attack with the element of surprise. If you have a level advantage from doing well early game but never shift out of lane, you'll have let your advantage slide.

Once you win team battles, start pushing as a unit.

Even if this all doesn't work, it's still possible to come back - but it comes back to putting yourself in the same kind of situations listed above. Try and bait someone into getting killed by a tower and then turn that advantage into a bigger one. Once you're on a power play (so to speak), counterpush, grab baron, finish farming those items, etc.

My favourite matches are the really close ones, where both teams are in bad shape, and inevitably you will take tower and inhibitor losses there. In my experience, there's a simple checklist for whether or not it's hopeless.

1. How many dead lanes (towerless) do you have? Usually they'll all be worn down at a similar rate, but if one or two are untouched, or even one has one turret remaining, that's a buffer that gives you reaction time, prevents the enemy from coming from there, and generally makes defence easier. I'll always feel more confident if there's some kind of buffer, even if it usually gets torn down in short order - that's time to organise, kill, maybe get in a push.
2. How many inhibitor towers are down, and what are the active ones like? Same principle as for dead lanes - it's additional reaction time. This is always the key to turning a match around - having as much time as possible to do it in. Just one down can happen even in a match you're winning, so isn't a huge worry. All three is cause for concern, as some champs have enough damage to chain between them before you can properly react.
3. How many inhibitors are down? One can be handled by a lone carry, though it'll force you to push along that lane or leave someone in defence. Two is harder, and I'd suggest consistent defence, maybe trying to BD an enemy turret to keep their attention split. Three is virtually impossible to defend against - it requires all the attention of every team member to just hold out. Coping with hostile champs as well means that the slightest mistake can result in defeat. The exception to this is...
4. How is their base? Even knocking out one hostile inhibitor is an enormous boon - one tends to think of it as an offensive tool, but if you've lost inhibitors, spawning supers is an excellent defensive weapon. It'll effectively cancel out one of your own lost inhibitors. I've even been in matches where all six inhibitors are dead.
5. How good at they at killing? If they have an overfed Yi or similar who can hit you hard while trying to defend a tower, or even if they are simply coordinated as a team, it's a bad sign. Learn who to focus down, don't take risks, and learn when defence is hopeless - don't bother running to a tower being hit by Yi if it's on low health, as he'll probably kill it and you.

I've won with 5 of our turrets and 1 inhibitor down + behind 15 kills, it's possible just very rare. Part of it depends on what teammates you have vs the other team, how fed the enemy carries are and whether or not you get any kills at all. If you're behind 15-20 kills and you can't retaliate at all, you're pretty screwed. But if you're behind 40 kills to 20 kills, you can shutdown their streaks for the gold bonus and you can work together as a team, you still have a chance.

One wrong move past level 16 or so can be /gameover. It requires teamwork. One of the failures of new players is not understanding to push and push hard and fast, often.
5 level 16+ players can drop a tower in 2 seconds. (Its infuriating when playing as a caster like Annie, or aniva where your dps on towers is awful, while your carries just refuse to drop towers, and end the game.)

Had a game last night, where i was playing Sivir. we were losing early. Other team had 10+ kills on us during the laning phase. They had outer towers down. Mid, they were still picking us off, and had several strong pushes taking out mid inhibitor. They were 15-18, while we were 13-15. But then we started working together better. My ult hit rank 2, and we started dropping them in team fights. stopped them from pushing, and caught up in levels a bit. 3rd team fight we beelined mid with sivirs team speed buff, dropped mid tower, inhib, and both nexus towers in about 30seconds, with our team still 16-17 with only one 18.

Depending on how many carries you have, it can be possible. If you have a hard carry, such as Yi, it might be a good idea to:

- Let Yi Defend. One Hard Carry + 2 Nexus Towers Vs 5 Champs isn't good odds, but it's good enough.
-4 champ push

OR

-Do it the other way around. Let Yi Backdoor with Mobility Boots.
-4 Champs Defending + 2 nexus Towers vs 5 champs isn't that bad actually.

This is assuming you are only losing by a margin of 10-15 kills, and that your teamwork is very good. It's always worth a try though: Split your team up, Defense and Attack Groups. Defense holds the fort while Attack takes Baron, and push. If the other team's teamwork is severely lacking, you can very possibly win this way.