I want to install https://www.gta5-mods.com/misc/law-enforcement-improvements

and many other police textures and also crime improvments mods,but they are somehow conflicting,or some of them change same files.How can i make them work,because nowhere says anything about compatability,will making them all work,just make problems or do they overwrite like everyone adds their content in to the same file?

I downloaded this file to check - it has a lot of data files such as peds.meta which each would overwrite the other from a different folder. It would have been better on the author's part if users were instructed to add specific lines of code to the same file so that there wouldn't be any compatibility issues like you said. For the LED lights improvements as another example, those would overwrite the sheriff textures if you tried to import it after installing the custom sheriff textures unless the .ytd's included those custom textures as shown in the screenshots.

It's a really confusing compilation of mods honestly, because it gives you options for each thing and that just doesn't work if you wanted to install everything. You'd rather it had everything as shown in the screenshots all set up in one folder ready to be imported into each .rpf as directed.

Ok ,so that's how it is working.