1. Replaced my Google G-Suite with Proton Mail and a self hosted Nextcloud The process was fairly easy: Just export all your mails and import them into Proton Mail. After that I've exported Google Drive data, contacts and calendar and imported everything into Nextcloud. This all took around two hours (including the Nextcloud setup).
The only "issue" was dealing with services where I use my G-Suite account as a login, but most of them allowed you to set a password so you can log in with email.
Nextcloud has amazing one click install apps that offer the same features that Google has (video calls, docs, notes etc.).
2. Removing Google from my Android phone For that I flashed LineageOS for microG. The great thing with this is, that you can install and use all apps you normally have but without having Google Services installed. As a PlayStore alternative you can use F-Droid and Yalp Store. Anyone who installed a custom ROM before will have it running in under an hour.
3. Securing my network with a PI-Hole and Proton VPN For devices like my phone, laptop and desktop I installed Proton VPN. As a browser for mobile and desktop I use Firefox with uBlock origin. For everything else (like "smart" devices etc.) I installed a Pi-Hole (basically Easy-List on network level) to remove ads and tracking scripts.
These were only the major steps that I've taken. So far I don't have any regrets about it and I haven't faced any limitations with the alternatives I use now.
If anyone has questions or ideas for further improvement, let me know.
Links: https://protonmail.com/ https://nextcloud.com/ https://lineage.microg.org/ https://protonvpn.com/