I'm bad at decision making. Help me improve

Ok, so I started playing Magic a couple of months ago, and I've realized I'm pretty bad at making good decisions in Limited (mainly). I recorded a few matches of Marvel Super Heroes Jump In to try to spot my main mistakes... could you also point out which decisions you think were wrong? (I know my deck isn't great, but I'd like to focus on the decision-making process, not the deck quality)

https://youtu.be/zzEmrMkeNFo

https://youtu.be/7aW_gdJ-nZM