Samsung Galaxy S6 is not turning on

Yesterday I changed the battery of my old S6 and it booted to life. I wanted to save old photos and videos from this phone. After changing the battery I could charge the phone and it even started. But after like half an hour the phone froze and turned of after like 10 seconds. After that the notification led in the top left just turned white permanently. I couldn't start the phone anymore. I charged the phone for a few hours and went to sleep. This morning the white light was off but the phone still doesn't turn on.

Has anyone ever experienced something like this or has some good advice? I tried all button combinations I found online but no response from the phone.

I only need my data from the phone, so it doesn't need to be a permanent fix.

Thank you very much.