not powering on after changing usbc connector and mainboard flex cable

My Phone got bent when i fell down, after opening the back i saw the flex connector at the usb c sub board was riped and the screen broken (i just want to get the data via samsung dex). i've changed the sub board and the flex cabele but now it wont start. with a charging cable with power read out it is charging with 3-7 watt, after a while power delivery gets activated and the readout drops to 0 watt and ocationaly vibrates.