SizeDoctor I want a solution ؟

Hello, I apologize for the translation because I do not speak English. I bought this device SizeDoctor, but it does not work for me correctly and I need help
The head of the penis comes out of the device after it is placed approximately 15 minutes or 20 minutes, and I tried all methods, but to no avail. Please help me how to use it correctly so that the head of the penis does not come out!!!

I occasionally have the same problem. Most of the time I insert my glans into the bell with the pump, the glans swells to provide a good seal, and everything is fine.

Sometimes, I get 15 or 20 minutes, same as you, and then the bell will slip off. Repeated pumping only works for a few minutes.

In my case, I have a large shaft and a small glans. Pulling a vacuum expands the glans so the ridge, or corona, makes a good deal inside the bell. But sometimes the glans doesn't want to stay swollen, and the bell slips off. I've tried using a smaller gasket, and that doesn't help either.

I haven't discovered any apparent reason this happens, but I've found that if I use a silicone cock ring to help maintain engorgement, the glans will usually stay swollen enough for the bell to stay on.

Also, the Size Doctor instructions recommend "a water-based lubricant." Those lubes dry out after ten or fifteen minutes, which help to keep the bell in place, though getting it off for pee breaks can be an issue. Saliva will also work. Silicone or oil based lubes will make it easy for the bell to slip off.

I'm up to 250 hours with the Size Doctor. There are certainly people with much more experience with the device, but they don't seem to post much.

Thanks for the answer