how long does it usually take for a non-professional to bulid a website?

I would like to build a full-functioning website with a database attached. It's going to be a student managing site which will have a bulletin board, some analytics of students work, hopefully a calendar too. I'd worked as a web designer and a sales*force admin so I think I can manage front-end stuff but I'd barely touched back-end codes and I find it very difficult :(

I'm kind of embarrassed to ask this..but how long do you all think it'll take for someone like me to finish this job?

• if you could inform me of some websites that are helpful for amateur web developers like me, then please share. Thanks!!!