If you download a template, as in this case you tend to just get the visible aspects of forms/search boxes, not the parts which make them work i.e. process the data. There's a short explanation here:
Your host is likely to have built in options, or not to hard to find php examples on the web, or find a site which will make the file online (just search on "website email" and take your pick). The issue is that security aspects are rarely well covered and forms can present a vulnerability. You could also use a remote mail service, where they handle the processing.
If you have real problems with search, you could just use:
Easy to implement and plenty of support.
Another option is to contact the site builder and see if they have forms ready, they often do (again security not guaranteed). You could then also ask them if they have a responsive version of what is a pleasant template. A photography site will see high mobile/tablet use, the current site not good for that.
Final point, don't know if you are on some form of free/ over crammed hosting, looks as if the host offers that but in any event, the server is not happy handling your very good but heavy images. You might want to make a move.