@JungerKrankl First of all, I recommend that you check if all patches have been installed properly. Base Game, every Expansion Pack and Family Fun Stuff Pack each have their own patch, but they are not all included on the disks; SimsVIP and Mod the Sims have all of them.
1. Base Game, University and Nightlife patches are especially problematic because they crash during installation, without an error message. So you should run each patch at least twice, and the second time it should tell you that The Sims 2 is already up to date. If the same patch keeps reinstalling itself every time, you got a problem. Mod the Sims has a program called GrumpyLoader which you can use to install those patches any bypass the errors, then run them normally and check that they don't install over and over again.
2. I am not sure if you have installed all packs already, but if you haven't, you might get a "This app has been blocked for your protection" or a similar error when you try to install FreeTime and newer packs. I have been able to get around that error by changing the system time back to 2010, so try that if you get the error.
3. Once everything is successfully installed, you will need Graphics Rules Maker to fix compatibility and increase texture memory and resolution. The Auto Detect option included is good enough, but do not let it disable Sim shadows as there is a mod that can fix them instead, created by Nopke on Mod the Sims. Also, if you have both integrated and dedicated graphics, you will need to go to your graphics settings in your system settings and make sure that the game (with the executable for the latest pack) is running on dedicated graphics; it will not do that by default.
4. If your game starts running out of memory (the highest it can go by default is 2GB), then you will need the 4GB Patch. Once you download it, move the executable for the latest pack (if you have everything, then it's Sims2EP9.exe for Mansion & Garden Stuff) to your desktop, run the patch and apply it to that exe. Then move it back to TSBin.
Hopefully the installation goes well. If you need any help, feel free to ask. Good luck!