All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
First of all, we ask Allaah to enable you to do good and increase your obedience and dutifulness to your mother. There is no doubt that you know the virtue of being kind and dutiful to the parents, so you should be keen on making your mother happy as much as you can by speaking to her and the like as this is one of the best acts of good deeds. As regards speaking to her while she is watching TV, then no scholar said that sitting with someone who is watching TV is forbidden. What is forbidden, however, is sitting with others while they are watching something forbidden; in principle, this is forbidden without a necessity and without denying it.
Ibn Taymiyyah said:
“If a man listens to disbelief, lies, backbiting, singing and flute (a musical instrument) unintentionally, and he was accidentally passing by a road and he heard that, then, by the agreement of all the Muslims [Muslim scholars], he is not sinful. But if he sits and listens to it and does not deny it either with his heart, his tongue, or his hand, then, by the agreement of all the Muslims, he is sinful, as Allaah says (what means): {And when you see those who engage in [offensive] discourse concerning Our verses, then turn away from them until they enter into another conversation. And if Satan should cause you to forget, then do not remain after the reminder with the wrongdoing people. And those who fear Allaah are not held accountable for the disbelievers at all, but [only for] a reminder - that perhaps they will fear Him.} [Quran 6:68-69] Allaah also says (what means): {And it has already come down to you in the Book that when you hear the verses of Allaah [recited], they are denied [by them] and ridiculed; so do not sit with them until they enter into another conversation. Indeed, you would then be like them.} [Quran 4:140] So Allaah considered the one who sits with them and listens to them without denying it like the doer. It is for this reason that it is said: 'The listener is an associate of the backbiter.' It was also reported that if someone sees a sin and hates it, then he is like the one who is absent from it, and he who is absent from it but approves it, he is like the one who witnesses it. If he witnesses it for a need or because he was compelled, then he should deny it with his heart; because the Prophet said 'Whoever amongst you sees an evil should change it with his hand (i.e. physically), if he is unable to do this, then he should change it with his tongue (i.e. verbally), and if he is unable to do that, then he should change it with his heart (by detesting it in his heart), and that is the weakest level of faith.”
Therefore, there is no problem in sitting with your mother while she is watching something permissible, and this is not forbidden. The problem is when she is watching something forbidden, like watching obscene scenes, for example; then, in such a case, it is not permissible for you to sit with her while she is watching that unless you object to her doing so. While advising her, you must do so in a gentle and soft manner and kindly apologize to her for not sitting with her.
As for playing video games: then the view that we adopt here in Islamweb is that it is permissible in principle, provided that these games are free from Islamic prohibitions, such as preoccupying someone from an Islamic obligation. Also, it should be free from gambling, music, and pictures of naked women, and it should not lead to enmity and hatred between those who are playing these games.
As regards just killing evil people in the game, then this does not make the game forbidden. Please, refer to fatwa 92138.
Concerning working in the post office, in principle it is permissible, but if you know that the parcel contains something forbidden – like alcohol, for example – then it is not permissible for you to do anything related to it, such as sorting and delivering it and anything that is a help for what is forbidden, because it is established in the sharee'ah that helping in the disobedience of Allaah is forbidden. Allaah says (what means): {…but do not cooperate in sin and aggression. And fear Allaah; indeed, Allaah is severe in penalty.} [Quran 5:2] Ibn Taymiyyah said:
“If a man helps in the disobedience of Allaah, then he is sinful because he helped in sin and transgression. It is for this reason that the Prophet cursed wine, its presser, the one who demands for it to be pressed, its drinker, its carrier, the one to whom it is carried, its server, its seller, its buyer, the one who consumes its price, its purchaser, and the one for whom it is purchased. Most of these, like the one who presses it, its carrier, and the one who serves it, help directly in drinking it. It is for this reason that it is forbidden to sell weapons to someone who will use them to fight in a forbidden manner, like fighting the Muslims or fighting at a time of tribulation.”
For more benefit, please refer to fatwa 124718.
Allaah Knows best.