Is it permissible to marry secretly with two witnesses, and with a temporary intention, for fear of falling into forbidden acts, if the family rejects the suitor for customary reasons?

The guardian (wali) is a condition for the validity of marriage, and it is not permissible to proceed with marriage without him. You can try to convince the guardian to marry you to the young man if he is religious and of good character, seeking help through supplication and some respected individuals. If that is not possible, the matter should be referred to the authority responsible for personal status issues. If the marriage does not take place, you must cut off the relationship with the young man, as it is not permissible for a Muslim woman to be in a romantic relationship with a man who is a stranger to her.