Post a game that you think exemplifies the issue.
Struggle as white player

I noticed that I also have a lot of games that end with back line check. I guess I need to be more observant.

Playing as white wasn't the problem here. You weakened your king and paid the ultimate price. f6 is pretty bad here. Moving the f pawn can be very dangerous, especially if your king is still in the center. Sometimes it is ok, but your game is the prime example why many people recommend following opening principles to improving players.
Edit: I am talking about the first game.

That is also correct.
Anyway, I see that you are playing 10 minute games. That is probably too fast for your rating. It is better to try longer games and take your time. You will probably decrease the number of one move blunders after some time and just with that you will be better. Follow opening principles, just develop as fast as you can and castle. And imagine the f pawn nailed to the board in the opening, at least before you get better.

You play much better as Black than as White?
As White, why not open with 1. a3 and pretend that you're Black?
Both games were problems with your play.
Black is easier because you are reacting to what white plays. Have the same mindset as white.
White does not mean attack. Be content to counter as you do with black.
One other thing, playing the f pawn to support the e4 or e5 pawn is generally not a good idea.
Hi,
Does anyone have any good hints on how to play as white?
I noticed that I win about 60% of my games as black but like 45% of my games as white, this is true also for my offline games. I feel I get stuck on developing my pieces and focus a lot on taking control of the center. Meanwhile my opponents play very aggressive.
BR
Johannes