You’re using position: absolute to achieve your current layout, and this is generally frowned upon. It will also make it nigh impossible to achieve any sort of adaptive or responsive layout. Most grid and layout systems work with floating items left and right, which I see your tables are. But there’s not much purpose to floating them when you then position them absolutely.
This is a good primer on basic layout approaches:
In the case of your project, I do think using tables to display the information makes sense, but you can enclose them within divs in order to control the flow of the layout.
It’s definitely true that there’s a lot of information out there, but if you’re going to use Bootstrap they do have pretty good documentation. Here’s their docs on tables:
If you combine that with their grid scaffolding system you should be able to pretty quickly put together a more adaptive version of what you have.
Keep in mind that Bootstrap will impose a certain aesthetic onto your application if you go that route.