what sever(s) can I use for remote server. After every update I have to download the whole blockchain again. copying .db file doens't seem to work anymore.
Copying the file should still work but there also one on bob:
http://bob.nem.ninja/nis5_mainnet.h2.db.zip (pretty recent i think)
You tech theoretically you any remote NIS as your server. There is no way for them to steal your founds. They could feed you bad data so maybe stick to the supernodes when the reward programm is up and running.
You can checkout the lightwallet and see which servers are listed there. Those should all be trustworthy.
working fine now. For a next update, do I uninstall / install, or can I install / update over the old version?