Newbie here; I need info on what I can turn off to speed it up

Specifically, first, I would like to turn stealth mode off if it will speed up our computers. We do not need anything beyond protecting on line purchases and finances. What is stealth mode, and is it necessary to protect our online banking or purchases? I am trying to speed Bitdefender up. It kicks us out of trusted sites, won't open trusted email links, VPN turns itself off. We seem to have a VPN premium trial of 20 more days, we don't want it but I don't know what will happen to our security if I turn it off. Will my Bitdefender Total Security have a VPN after the trial period? If it switches to a different VPN, do I need to turn it off and on? Any answers to any of my questions will be helpful, Thanks, Sue