Climbing MMR, i have lots of questions for those who wants to answer to a 2.5k noob.

Hello,

So i have been playing this game for quite a while. I managed to get my rank as 2.5k but my problem is i get to 2.6k and then drop back to 2.5k this happens constantly. Sometimes i lose 6 games in a row, sometimes i win 6 games in a row. So i have a couple bit of questions.

1)Is there a specific lane that i should focus on to climb mmr? Or should i keep playing what i am best at it ?

2)On dotabuff, there are games like http://www.dotabuff.com/matches/2166066171 but there are matches like this http://www.dotabuff.com/matches/2163918178 . Which gets me quite confusing, i sometimes play good but it all tears apart because of one bad guy, or one simple mistake.

3)Should i keep on trying at climbing ? Or keep playing untill i get a state where i can dominate everyone in my mmr level? I wouldnt say that i am a 2.5k since i have played with a friend with 3.5k mmr and still did quite good.

PS. This is not a hate post or a shit post where a noob says that he cant climb. I really want to hear constructive critisim and improve my play and mmr. Also i am not a native speaker, so sorry for any mistakes on grammar etc.