Chainsaw tightening itself

I got a new chainsaw in summer and used it to cut down about 10 tree stumps in the backyard. After the first 7 it started to get incredibly dull so I put some force on it and i remember the chain popping off. Put it back on and got the job done. Today as I were to use it again I noticed the chain was way too tight and I thought maybe that's why it felt so dull last summer.. so loosened up the cover.. tried to losen the tension screw but it was stuck.. had to use quite some force to get it to move after that it would screw normally and the chain was loosened up. lifted the bar up, tightened it just a tad and put the cover on while lifting the bar up. Here is where I went to check if the chain would spin freely and it did, at the start.. some parts of the chain were harder to move than others that would just glide.. Decided to give it a go and right away i saw a spark coming from the top as soon as i tried the cut (birch) and the chain would get so tight that it would stop moving even when revving the engine and get so hot the saw started to smoke.

What do you guys think the problem is and what should I do? Thanks!