Use either the old:
https://takeout.google.com/
...or new Google Photos Takeout:
https://takeout.google.com/takeout/transfer/custom/photos
Transfer a copy of your photos and videos to iCloud Photos - Apple Support
A few months ago I briefly tested the new Google Photos takeout to Apple iCloud Photos. Long story short: it was slow and it transferred images and movies from Google Photos quite fine to Apple iCloud Photos. The times might be off because Google Photos seems to use UTC instead local time. None of the metadata edits done in Google Photos or Apple iCloud Photos could be downloaded with Safari browser to the Mac desktop.
If you want to do it properly, use the old takeout with .json sidecars and workarounds for UTC vs local time, location-less images (incorrect GPS 0.0 in the Atlantic) and incorrect names in .json sidecars (DSC00041(2).JPG vs DSC00041.JPG(2).json). You can join .json sidecars to the image and movie metadata either with exiftool or GraphicConverter 12.
Google seems to have recently slightly changed the old Takeout so *.json seems now to be named *.supplemental-metadata.json so you might need to edit exiftool commands accordingly and GraphicConverter might not yet be updated for that change.
https://exiftool.org/forum/index.php?topic=12905.0
.json sidecars carry metadata edit info done inside Google Photos, so you you can ignore them if you have not edited metadata (dates, captions, locations, ratings) inside Google Photos. Then you might just download the images and movies from Google Photos albums and then manually upload them to Photos library and sync to iCloud Photos.