What should I do after learning of the prohibition of purchasing in-game currencies and loot boxes due to gambling: should I get rid of the account that contains both forbidden and permissible items, or should I benefit from it? And what is the ruling on free loot boxes that the game offers as a reward for a certain achievement; should I accept and open them or not?

You are not obligated to dispose of the account, but you must avoid transactions that involve prohibited gambling, such as purchasing "loot boxes." However, accepting them as a free gift is permissible.

We draw attention to the importance of preserving time and not wasting much of it on what is not beneficial; for there are two blessings concerning which many people are deceived: health and free time.

"The feet of the servant will not move on the Day of Resurrection from before his Lord until he is asked about five: about his life, how he spent it; about his youth, how he wore it out; about his wealth, from where he acquired it and in what he spent it; and what he did with what he knew."