See files in partition/volume I can not reach

Hello there.

I wanted to do an update of the OSX on my MacBook. The update went wrong (I do not know the reason). My MacBook could not startup after that. I started the laptop with command+R - and then I could install the OSX latest version. I did that but now the OSX seems to be on a different volume than my other files.

I cannot get to the files anymore and my laptop has a clean install... See attached file with the situation as it is now. https://imgshare.io/image/hBrJZ

Would like to have 1. the latest OSX and 2. access to my files.

Does anybody know how to solve this problem?

Regards, Martijn