hi !
when i logendin in nextxloud, Version 12, i must wail long time, more then 2 min!
its my Linux Server, Ubuntu 16.04, Dual core, 16MB ram.
Philip from Swizerland !
Hope your 16MB ram is 16GB ram. If not … there you have your problem 
What does your nextcloud.log, http error.log say?