I just started this game a few weeks ago and I want some tips for improvement.

You can check my match history(it's not that good) but i don't consider myself to be a noob, nor a pro.

I use master yi as my main, and sometimes fiora or olaf.

there are usualy a few problems in my game
1.i sometimes make silly mistakes early game
2. i get put with feeders/trolls/leavers
3. the enemy team are super pro(i suspect they are smurfs)

also, i can not seem to solo top properly and i usually end up feeding.

if I ever do get fed, I sometimes also fail to carry the game. I usually get focused and die, and my whole team dies too... Or sometimes my team doesn't even listen...

currently have 20 wins and 25 losses

are there any tips for these champions or should I try some other champs?

im just asking for suggestions...

All of these characters are solo top and/or Junglers.

Yi on top is trash, so don't play it. Play him as a jungle, he is better that way.

1) In lane, waiit for your minions to get the enemy minions low then last hit it for the gold. Don't push your lane.

2) Buy wards, and ward the river where baron is at. one ward is enough. If you do that, you can't get ganked.

3) You just have to have knowledge off the game.

4) Some runes help ALOT. For example check my rune pages for Olaf. If you go with these runes, the enemy lane will have it really hard to beat you later on when you get a Wriggles.

5) As Yi, come in later after the team has burned all of their spells. Then ult, alpha strike to the enemy AP carry or AD carry and kill them

6) Call MIA's, usually people get mad when they get ganked from other lanes when you didn't call MIA. This however, is their fault because they overextend, and have no map awareness. However, call it anyways because they will get mad at you

7) Have map awareness. If for example you are top, and there is a small fight happening near the river where Baron is at, go down their and help out your team.

But I would say, try to learn how to jungle as Yi. He isn't a good top character.

Falco has some solid advice, but even with map awareness you need to call MIAs. Only you know if the Twitch in your lane is really MIA, if I didn't see a Twitch on the mini map and just stayed at my turret all day, I would be effectively zoned. This doesn't just apply to stealth characters either, this applies to people who like to sit in bushes or roam.

Following are some tips that I believe I may be able to dispense (give you only have like 50 games at most):

1) Knowledge of the champions that are on your team (their weaknesses, strengths, ganking ability)
2) Knowledge of the champions that are on the other team (their weaknesses, strengths, who to target, who to leave off till later) [There are a lot of champions, 93 going to be 94 so it takes time and playing and playing to get familiar)
3) Remember jungle respawn timings
4) Ward. Please, this is most important. You can't win the game if you don't have control of the map 9 times out of 10. Even experienced players are guilty of not providing vision. You can't react effectively to the enemy if you don't know what they are upto
5) Do not attack the tank in a team fight first. Go for the squishies. It seems like such a basic thing but you'll be surprised how silly people can be.
6) You will not be good at every champion. Experiment and then pick a few that you are most comfortable with. Make anywhere between 1-6 your 'mains' (this depends, of course on your dexterity)
7) Do not rage. Be generous and understanding to others. Your teams might stink sometimes but hang in there. Be nice, don't troll. Do NOT AFK or leave for stupid reasons. Report trolls.
8) The game ain't over till its over. So don't really give up.

I typed more than I wanted to but i hope there's something that can be learned from this.

Have fun LoLing.