How can I stop committing sins and transgressions, such as masturbation, and sincerely return to Allah, especially with the repeated breaking of vows and the feeling of despair?

The greatest joy for Satan is to deter a servant from repentance and to make them despair of it. Allah is Forgiving and Merciful; He accepts sincere repentance no matter how often the sin is repeated, and the one who repents from a sin is like one who has no sin. So do not despair of Allah’s mercy. Treat the sin with sincere repentance, and no matter how many times you return to the sin, return to repentance and do not despair. Increase in good deeds that wipe away sins, and have a good opinion of Allah. Strive against sins and seek help through supplication, the company of righteous women, and listening to beneficial knowledge.