Hero has around 400€

Villain is sitting on the table for 20 minutes with 245€ and is a card dealer at the casino playing in his free time.My experience is that most card dealers i know are pretty bad at playing poker.No other information about his games.

MP raises to 7€, hero 3bet to 25€ with JdJh in CO, villain calls on the button, mp folds. HU to the flop.

Flop 873 (pot 60€)

Hero cbet 30€, villain raises to 70€, hero calls.

Turn 873T

Hero hecks, villain checks behind.

River 873T9

Hero valuebets 70€ and villain moves allin for 150€.

Not really sure if flop play was correct and what the correct play in this hand is against an unknown.
I am struggling with similar spots when getting raised on such a flop with overpairs

What did you expect him to do when you bet the river? Shove was standard here given pot size, and I dunno what you expected your small bet to accomplish.

After he checked back the turn i thought he could have QQ or 99 because at 1/2 most people dont 4bet QQ and often cold call a 3bet with 99 and TT. I wanted to get a little bit of value or a crying call in case he has QQ or 99.

I just dont know whats best on the flop when i get raised on such a flop. Or is just calling standard?

River is shrug/call. Between hands you win and hands you chop you can't fold given those odds.

As for dealing with the flop, this is a painful situation against an unknown. With a better read this could be anything from a fold to a raise depending on how many bluffs/sets/draws/overplayed hands are in his range and what he calls with preflop. Against an unknown I probably end up playing the flop the same, too soon to give up an over pair but reraising just folds out his draws/over plays/bluffs. I would likely check the river and call any bet after backing into a straight.

I think flop is fine. You could make a tight fold, but these raises tend to be weak top pairs and overpairs trying to "see where they're at" Against a known nittier player I can fold it. Assuming he would 4-bet KK/AA, then you are ahead of a lot of his bad value raising range.

The river is better if you have the J, but I think I can call this off, his line is so full of **** at this point. There are just no real club hands that make any sense here, other than a random flop bluff that backed into something.

I agree with the first part of this common.
you could consider folding on flop after being raised, if he is nit or if he does not have much money behind

Shrug and a call. Sure he could have flushes, but there really aren't many combos given how the hand has played. A8/56 are the only reasonable flush combos I see, unless he bluff-raised flop with total air and backed into the flush. He should have QJ like never too. You're getting over 5/1 with the top end of a one card straight, gotta call it off here.

Call river. Line is weird for a rivered flush.

Why is 3B shoving flop bad? Villain only has like $160 behind or something.

I called and he had KJ