Hi @troetenhubert,
I probably don’t qualify as your definition of a better player but I’ve had a look at those hands anyway 
First hand: I’m not sure what you expected from your open raise but I’m truly surprised you even got one player to fold.
Postflop: Again I don’t know what you expected - that bet size looked more like you were building the pot based on a draw. Villain obviously saw it that way as well. Regardless of that, he re-raised and that is your warning that he isn’t going anywhere! When he re-raised, I think you only had 2 choices - fold or shove. It’s going to take a lot of convincing to get him out of the hand now and a 3-bet is not the weapon of choice!
Your immediate question should be: Does he have 3 of a kind or not? … if not, then you are shoving. As you found out, there’s too many things that can happen on the trip to the river.
Second hand: It’s safe to assume that Villain has a pair or a big hand. I’m not convinced that A3s is strong enough to even enter the hand here especially when you know (or should know!) that there’s 5 people coming along with you. Anyway, you bravely entered the hand and the flop shows a low flush and, possibly, a straight draw. Villain bets and you call. Not too bad.
You hit your ace on the turn and there’s a flush draw on the table. You’ve got the nuts right now and you could easily miss the flush on the river. As you learned in the first hand, the river behaves in mysterious ways and can just as easily break you as make you. I would have bet at least the pot first in and either shove or fold if he re-raises depending on my read on him. Looking at the hand from your point of view as you played it, I would have said that V is still on a draw or a single pair and so I’d raise and shove to a re-raise.
You decided to slow play and villain raised you. You’re trapped by your own cleverness now. Villain may have 2 pair or 3 of a kind already, drawing for a straight, drawing for 2 pair or 3 of a kind and he may be drawing for a flush. He’s got a lot more outs than you!
The only upside here is that if you hit a flush or another ace, villain will almost certainly put the rest of his stack in.
The river shows a jack and villain shoves? You’ve got a single pair against what exactly? It should never have got to this point and you really should fold. In all fairness, I don’t know if I would have been strong enough to fold under your circumstances!
I’m not at all suprised at the result.
Third hand: You call it “standard open raise”, I call it issuing a challenge that not many can resist!
On this occasion I’m more than happy to concede that the villain was wrong to even enter the hand and even more wrong to call your 4-bet!
You got aces and he got something on the flop and shoved. I think you were right to call the shove this time and it was just a bit of bad luck that he hit 2 pair.
I think your biggest mistake, just from these three hands, is that you seem to expect cash game behaviour from low stakes, free chip players. If you start expecting that you will be get called and 3-bet by nearly any 2 cards, then these sorts of hands will stop surprising you
Hope this helps!
Regards,
TA