Frameworks choosing for simple website constructor

I learning web dev and I have to make a simple website constructor – user logs in, fills several forms, shoose design template and then get page on my domain, something like website-constructor.com/user-generated-page/ – according to his/her settings.

The question is – what frameworks I’d better choose for this job? User part I’ll do ok with javascript, but what is better for server part – generating a page? Maybe there are some special tools for such website?

Cheers, thanks a lot!