Thank you, I have checked out G-Suite.
The price of $300/year for G-Suite Enterprise is per user. G-Suite Business is $120/year/user. Therefore, it can get very expensive IMO.
Thank you for your advice and for taking the time to answer.
I will make a cost comparison based on my needs and then decide.
Anyone else reading this, who runs/ works at a startup: it would still be interesting to know how you set up/ are setting up your infrastructure and why.