I would like to buy Microsoft Office 2019 (full version) shortly. Home and student is only for a PC. If I buy a new laptop, do I have to buy Office again, or are there other ways to transfer it to the new laptop?
Buy an office suite with a license for 3 PCs. That should be enough.
No, you just have to log in to the laptop or office using the Microsoft account and then you can simply install it
You just have to buy more licenses.
On ebay there's an office key for 5 eur, sorry 9.99
Yes, if you remember the login data from Microsoft.
Office pro plus is cheap here: https://www.rakuten.de/produkt/microsoft-office-professional-plus-2019-2969614645
and here is the explanatory video: