My Altium Designer does not show any violation, even if I place 2 components right above each other. Im quite the beginner at PCB Design, but does someone know the answer to my problem?
If you expect this to happen as soon as you create a violation, then the malfunction could be because the online DRC was turned off. It slows down the tool a bit, but on small designs/fast machines it's not a problem.
Alternatively you could use the manual DRC check, which is good practice to run after schematic chances and once you want to check the status of your PCB design.
Above all, it's important to set up good design rules for your manufacturing technology. Check at your PCB manufacturer which widths/clearances they allow, such you can design for that. If you don't know how all of this works, it's best to work with the defaults and do not delete any rule.
The design rules are there not to annoy you, but as a check that the board can be manufactured and is free of obvious mistakes. However, in my personal opinion, for hobby boards/very quick prototypes I would mostly ignore the silkscreen errors as I only really care about the copper and solder mask in those cases.