When something has such a strong hold, sometimes it is a a soul tie or ancestral sin that is the doorway to a more powerful, seasoned demon which creates stronger temptation than it normally would (generational curse or spirit) so it is harder to resist the enemy. This is why you see i.e. alcoholism or adultery run in families generationally. Jesus has power over it and is able to deliver, but we have to claim the promise, close any doorways, and then resist the devil. Another thing that might be blocking deliverance is holding a grudge. I had this problem in the past, I used to hold some grudges against people and God would not forgive and deliver me until I let of go of my "book of debtors". So read the prayer, then meditate prayerfully on these things first, is there any such thing before you go to Him to ask for deliverance. It might not be any of these, but it cannot harm to rule them out. I pray that Jesus will reveal the reason to you that you keep being oppressed, amen.
And now we pray in Jesus' name:
Father in Heaven, uphold your son franswa and keep his foot from falling. Deliver him from the demonic oppression. He confesses and repents from his sins and also sins of his ancestors and renounces them (name these as you pray to Jesus if you know any particular sin) and we trust You are faithful and just to cleanse us of all unrighteousness. In Jesus' mighty name, we break any soul ties that are not of God and bind and cast out any spirits from franswa that are not of God, which had the right of entrance due to these ungodly relationships. We also renounce any generational spirits and curses, cast them out and cover them in the blood of Jesus. We cover franswa with the blood of Jesus and ask for Your holy angels, God, send your mighty warrior angels to defend him and fight on his behalf. In Jesus name, we renounce any sins of the ancestors in franswa's family and leave them at the Cross, in Jesus' name denying these demons the rights to dwell in his life and perpetually disturb him. We cover the enemy in the blood of Jesus and send him in shame to serve as Your footstool, God. We trust You are faithful to finish the work You started. This child of Yours is hurting and desires to serve you and he loves you with all his heart. We plead Your healing hand over him. We do not call You slow to deliver, but activate Your readiness to battle evil. In Jesus name, AMEN... Praised the LORD who is our Savior!