Should I abandon my friend who became angry with me for quitting working with him in an internet shop that contains things displeasing to Allah and many temptations, or should I continue to visit him hoping he might return to his former self?

If you abandon work because of unlawful acts, you will be rewarded, and Allah will compensate you with something better, for abandoning something for Allah's sake is a sign of complete faith, as the Prophet, peace and blessings be upon him, said: "Whoever loves for Allah, hates for Allah, gives for Allah, and withholds for Allah, has perfected faith."

If your friend stipulates the continuation of friendship upon working with him in unlawful acts, then there is no good in his friendship, and you must advise him and warn him of Allah’s punishment.

It is not permissible for you to frequent places of vice or mix with their people unless it is for the purpose of condemning their actions.