HelpClient vs server side question

Hello,

I hope this is the correct place to post this. In the past I have seen GTA5 hacks where people have used the cheat engine to multiply the money / RP earned during races. I would like to do something similar to hack an old DnD game, nwn 2. I have hit a wall and I am reaching out for guidance on next steps from those far more skilled than me. In single player I can use the cheat engine to multiply the amount of experience I gain every time I kill a mob via the code injection feature of cheat engine. However I do not know how to get a similar effect when when I play online and my character is stored on the server side. There are a few private online servers people still have up. All I really want to do make it so instead of gaining X experience for killing a mob I can get 100X experience or something like that.

1) It is my understanding that the GTA 5 character info is stored server side. Is this correct? If so can someone explain to me the basic concepts how to manipulate money and xp in GTA online when character data is stored server side?

2) When hacking xp on a server sided game do I actually need to hack into the server or can I just somehow influence the data being sent by the client to the server to make it look like I gained more xp?

I am ok with C# and the Cheat Engine but far from an expert. I have no idea where to start when a character is stored server sided and just looking for any tips. Thank you very much for any guidance. :-)

In the past there were more then only 1 Method how to do it, at the beginning you could just change the RP Value in CE to what you want and gain some after it will change it to the Value you set.
Then the other most used thing were then Tuneables.
On them you could change any Multiplier we knewed and get the Effects you are searching for.

Both detected now.
You can change the RP Multiplier to 2 and the Cash Multiplier for anything (Race, Parachute, Survival) so high that the Output is not over 100k.
Otherwise it will result in ban.

The greatest Issue of GTA is, they trust the Client (every Programmer knows that, never trust User Input, but R* did)