Wordpress custom titles

Wordpress custom titles

I am trying to add custom titles to my wordpress theme and I am having a
bit of trouble.
I know I can use AIOSeo but it adds so many functions that I wont use, so
I am trying to make this on my own.
I have added a few inputs in my theme settings page (one for home, one for
categories and so on) and I would like to be able to store my title
structure in those fields.
I have managed the storing part, but I cant make the proper output.
For instance, if for the index title I store "get_bloginfo('name')", when
I echo it, it says "get_bloginfo('name')" and not "My blog name"
How can I achieve that?
BTW, I am trying this
if ( is_page() ) {
echo $pagetitle;
Best regards!