What is the name of the detection? If it’s it’s a trojan, it can’t be repaired as the entire file is the trojan. The avast detection will give that info. Trj
Your best selected option is move to the chest, the repair button is normally only available if it may be possible to repair. The worst option of the three you list is move/rename as this doesn’t put it in the avast chest, but the \DATA\Moved folder and ads a .vir to the original file name, but there is no retained information on where it was originally (which there is for files/viruses sent to the chest).
Trojans generally can’t be repaired (either by the VRDB or avast virus cleaner), because the entire content of the file is malware, so it is either move to chest or delete, move to the chest being the best option (first do no harm). When a file is in the chest it can’t do any harm and you can investigate the infected warning.
The VRDB only protects certain files, mainly .exe files, it doesn’t protect data files or all files, it is not a back-up program, so there are going to be many occasions where repair won’t be an option.
Only true virus infection can be repaired, e.g. when a virus infects a file it adds a small part to it, provided that file is one that avast’s VRDB would monitor and you have run the VRDB, then it may be possible to repair the file to its uninfected state.
However, for the most part so called viruses, trojans (adware/spyware/malware, etc.) can’t be repaired because the complete content of the file is malicious.
There is no rush to delete anything from the chest, a protected area where it can do no harm. Anything that you send to the chest you should leave there for a few weeks. If after that time you have suffered no adverse effects from moving these to the chest, scan them again (inside the chest) and if they are still detected as viruses, delete them.
Don’t touch anything in the System Files section they are back-ups of important system files. The only area of concern is the infected files section of the chest.