Hello, I'm a casual Heroes of the Storm player for a few years and my first start to Dota 2 was 1-2 years ago and the game was too complex and I was only be able to play some New Player Mode matches, they were easy but afterwards I learned that those matches were against bots. Anyway I decided to give a chance again because this game seems really cool to me.

I tried some workshop bot games in Unfair difficulty with Axe but ranged bots demolished me so bad, I watched some guides and decided to move Unranked All Picks game even though I have some hesitation but I pick support role this time due to not have to farm and would have the opportunity to see how game flows. I played two matches with Crystal Maiden, both lost but in first we had a disconnected player and in the second one we have a really underleveled man. Even though this losses the matches were really fun and I'm willing to continue the game.   
  
But I have a few questions:  
  
1) Both of the matches, our safe lane was empty, in the first match he/she got disconnected but no one was willing to fill that lane, I tried to cover then I start roaming with team due to being support. Why people leave lanes empty? It's because of I also matched with beginners and they don't know what to do or there is something different?

2) How can I understand that I play good or bad? I attached the screenshots, according to KDA and damage done it seems I'm not bad but we just measure the game with this?

3) It seems support is the safest position to begin but is it the true one? I was actually willing to play Axe but even against unfair bots I was struggled then I jumped into unranked with taking all risks...

(Chat was turned off due to not affected by toxicity but I feel comfortable while playing and people emote me well, so I'm gonna turn it on my next games.)

Sorry if that's too long and thanks in advance.

How can I understand that I play good or bad? & Why people leave lanes empty?