How to play better in time pressure and effectively eliminate simple blunders?

Hello,

I cam back to chess after a long break around 6 months ago and I have improved since then in many parts of the game. Anyway in the past 6 months I have participated in a number of tournaments (15' time controls) and considering I'm unrated I've done well enough, but I have always felt unsatisfied. Most (if not all) of my losses came out of a postion better or much better for me, but when I have ~2 minutes to make precise moves or convert the advantage my opponents do better than me. Here is one example of a game like that against a FIDE Master:

Anyway that theme has been recurring in my games, more often than not i can outplay many opponents in the opening and middle-game, but endgame is associated mostly with time-pressure in my case (I don't plan on playing with classical time controls in the next year) and time-pressure is sth I do not handle well. Funny enough in our next encounter I decided to play faster (I had likely more knowledge about this opening) and I managed to win a game against the same FM, but only because he applied incorrect defense, so this time I had a lot more time on the clock, but I cannot say I played best moves (especially one blunder that I was fortunate he didn't exploit):

So although I managed to win in the end, I must say I like my first game better, I thought I achieved a winning position there in a much more "legit" way. 

Anyway I'm regularily studying tactics (5-10 simple ones per day), but I still catch myself making terrible blunders in time pressure or when I make a hasty decision. In conclusion I am open to all suggestions and if you give me an advise, please make it a practical one ( for example if you think studying the endgame is most important to this, please also say how exactly I should study it).