Strong flop, lost heads up, what did I do wrong?

Little hard to read through this, only thing I saw was 75o. Easy answer Fold pre!

You should be playing with full 100bb stack whenever possible. This hand is very weak but with the two limpers I think it is not a huge mistake to complete this from small blind.
Flop and turn seem ok.
OTR I would recommend to just check call. Or even check fold? The board is paired and any Kx will beat you now.
As played, river raises are often very strong and you could fold. This is a limped pot so villain is probably a fish and playing very unpredictably.

You can fold preflop. Calling the limp is not that big mistake but if you have a thinking player in the blinds and he raises you have to fold.

On river every Kx, 3x, 88+ beat you so there is no need to invest more.

Have this simple rule: Never play for all your money in limped pot without the nuts!!!

You can't possibly fold two pairs in limped pot

In fact, you can't possibly fold even a pair in a limped pot. After all, they limped. They must have very weak holdings.

No, really. You have to be very lucky to win this pot - ever. Your hand might have some value as a bluff catcher, but just checking and folding at some point wouldn't be that bad. You typically win a small pot (when they fold flop) or lose a big one (when they call flop).

Key observation: That turn card didn't improve your hand unless they hold precisely 66. It adds a few outs though.

"Was I wrong assuming that Pokerjoke was bluffing, who the hell keeps calling with a Full House on the flop??? "

Calling with a boat is a normal play in this situation, imo. Why would he raise? There is almost no card that can hurt his hand and a raise on this board would look really strong and make most hands folds. With a hand like that, in a limped pot, with an aggresor, you want to keep as much hands in as possible and let them keep firing bullets at you. If there was a lot of action pre, you can raise because people might have strong hands that will pay you off but in a limped pot, people are usually very weak and bet / bluf with weak pairs or worse. Keep them in the pot a long as possible

Thanks for the answers. I thought lets look at the flop as I was in a late position. But then with a pair of 5s I should have checked and then folded after Pokerjoke would very likely had raised the pot.