See this thread
https://www.phpbb.com/community/viewtop ... &t=2147210
Iv'e had forums in the past on my own websites and spam is a big problem, it's probably that that's slowing it down as much as anything, i'd try upgrading to the latest version first
https://www.phpbb.com/community/viewtop ... &t=2389426
There may be better means of blocking spammers on the newer version, (I see the footer on this board is showing a 2007 version)
Also here is a youtube vid showing how it's done
https://www.youtube.com/watch?v=ZF0F1ZAIsz8 I have done this in years gone by and although I still have a couple of sites, but there'd be re-learning curve if i had to do it again.
A pro-website company should be able to move this in a couple of clicks, it's what they do day in day out, phpBB is a popular forum and should pose no problem for them, alternatively I'd post the question on their forums and see if anyone wants a couple of quid to move it for you.
PS it's definitely the speed that's losing users, I use both social media and forums differently, and there's still a place for these, I usually check on here at least once a day to see if there's anything interesting and I also check on the Fairey owners too, but the speed here is now making it too painful to stick around long, whereas in the past i'd look at old posts and pics.
If you're really struggling let me know if I can help (notify me on here that you've PM'd) but tbh there are more qualified folks than me to move this, but it's not complicated if you read the instructions well and take your time.
Good luck
Phil.