Dpc around window

[PotatoSoup]

Thank you so much for reading this - please help! The DPC around my bathroom window is shoddy and there's a big gap between the metal lintel and the aerated block. I'm planning to stick Gorrila waterproof patch and seal tape to the window frame and dpc on the sides of the frame and the bottom. Then stick the tape to the metal lintel and the frame. Is that insanity or ok? Please someone tell me?