PokerTracker

Let's say that we want to know if our flop cbet/call line is +ev. At first we filter for the particular spot and get listed all hands where we've cbet/called. At the bottom we see the sum over all filtered situations - assume that it's negative. One might think that we are losing money in this spot because the expected value is negative, but that is not necessarily the case. If we lose less money by doing the action than folding, the action is correct and +ev (compared to folding). So how to figure out if some action is +ev? Is there any stat that keeps track of the money invested so far?

PokerTracker 4 doesn't calculate expected value (EV). There are statistics that calculate adjusted equity but only for all-in hands against your opponents specific holding:

Guide: All-In Equity

sorry, this is not what i meant. instead of ev i should ve rather used the term winrate.

i will use a more specific example. say we want to figure out if our turn calls with a toppair type hand is profitable. you filter for this spot and have for example 10 situations. your overall winrate shows -10bb. is your call bad tho? not necessarily. you have to compare it to the option of folding. folding results in losing all the previously invested money, say that's -20bb. therefore calling on the turn is profitable and should be done, despite the negative winrate of -10bb.

so my question is, if there's an option to keep track of all the money that was invested for all the 10 different situations?

There isn't an option for that but that might be possible with custom statistics depending on what you want.

For bet-call sitations I am using the build-in report stats "game currency bet preflop / bet flop / bet turn / bet river" together with the costum stats "pot sizes on each street". However, I've difficulties when it comes to bet-raise-call sitations, because I can't reverse engineer the exact bet/raise sizes. The reason is that game currency bet x means actually the total amount of money that is invested by one player on one particular street, so when there was a 3bet situation it shows the amount of that 3bet and not the first bet of that player.

That will require custom statistics - see this guide for the basics on custom statistics creation and this guide for a deeper walkthrough. The size of a players bet on the flop is cash_hand_player_statistics.amt_f_bet_made, the size of a players first raise on the flop is cash_hand_player_statistics.amt_f_raise_made and if they make a second flop raise it is cash_hand_player_statistics.amt_raise_f_made_2. If you need the bet/raise sizes faced by the player (amounts need to call) those are cash_hand_player_statistics.amt_f_bet_facing, cash_hand_player_statistics.amt_f_2bet_facing, cash_hand_player_statistics.amt_f_3bet_facing and cash_hand_player_statistics.amt_f_4bet_facing.