Sure I can install a forum script for you. You just need to tell me the name of the forum script, and I will install it at your site's /forum directory.

Update: I fixed your site for you, it seems that your theme settings is incorrect, but the problem is gone now, you shouldnt receive smarty error anymore. It appears that the uppercase('Bookstore') and lowercase('bookstore') tend to cause trouble for your site, you have to be careful when entering this value in ACP.

I'm so sorry.
I broke it, again. I don't know what happened.
I tried to open the site and it didn't work, so I tried to fix it.
I failed.

Well what did you do before you broke the site? When I accessed your site last time, it was normal. I scanned your site, and I didnt find anything wrong with the script files.

Edit: It seems to me that you messed up with the styles. I set the default theme to 'main' and 'green' and both are working(although the dropdown menu is broken, but that's another problem), while if I set the theme to be bookstore it will not work. So I wonder, did you modify some files in /css or /templates/bookstore folder? This may be the cause of your issue, but note that helping you with custom CSS is beyond my responsibility of support here.

It's something with the theme files.

Yeah I figured. If I set the site theme to be 'main' or 'green', your site is working, but 'bookstore' is not. Did you modify the files in 'bookstore' theme, or the /css folder?

The bookstore folder. I reinstalled it over and over again.

Well you see, I was asking you what you did on your site before you started to see blank page. Was it working for you before you installed bookstore over and over again?

I don't think so.

I can login, but once I login it's messed up.

Its messed up after you logged in, because the theme for guest is temporarily set to 'main'(which is working), and the theme your account uses is 'bookstore'(which is not working). I fixed it for you, by temporarily setting your account theme to 'main'.

Anyway, the 'bookstore' theme was working for you before, last time I checked. Why did it stop working all of a sudden? Did you change something about it?

I must've. Thanks for all your help!