I would first approach this problem by first trying to convert as many apps that you have into a Foss alternative ( you could use this site to find the alternatives: https://alternativeto.net/).
Then if I was comfortable enough I would later on try flashing a custom rom like lineageOS (I would recommend doing this with a second phone if you have one, like a older phone to get used to the OS since it is a bit different and if something happens you have the original phone as a backup).
Then I guess the final step would be to isolate your work apps that aren't Foss like WhatsApp into a separate environment with an app like shelter.
Edit: Also try to not rely on google services as much as possible by using alternatives like protonmail/tutamail for email and other search engines like startpage, duckduckgo and searX (or searXNG, I do prefer more this one) (searX/XNG instances being the best search engines out there)