First, yes, you need to learn PHP. You can pretty much don’t bother with rest of answer until you have PHP basics (at least) down.
Now let’s talk about WordPress and Bootstrap relationships.
WordPress provides template tags. These are PHP functions that are meant to be used in template files. There is a lot of them, to output all kinds of things and data WordPress deals with.
Bootstrap front-end framework. It expects you to output markup in a certain way to achieve certain baseline look and functionality, to serve as foundation for more individual solution.
So how well these two get along? So-so at most. It varies plenty how eager WP’s specific template tags are willing to play nice and output that specific markup Bootstrap needs for specific case. Sometimes it goes well, other times it’s a mess.
The good news is — due to enormous popularity of both there is overlap of enormous amount of people willing to fall on this sword and try to figure it out. There are dozens of Bootstrap themes for WordPress around.
What would I suggest next (after learning that PHP part)? Go look one of those themes and start taking it apart. Best case scenario it will allow you to convert your existing site, already using Bootstrap, quite easily.