I've mostly worked with Springboot framework only with JSP to cover the things I need for the website part. Now, I've got a project to do that mostly revolves, if not all, around the website and I have a couple of questions. 
Just to be clear first, I don't have experience either with Thymeleaf or Angular so whichever I pick will be the first time (I think thymeleaf syntax would be easier for me to handle). 

Ok so the main goal in my mind is not to render the whole page every time I load data from the backend, so I figure I would have like a header/content/footer parts where every time I click something only the content part would change. Also, I would like the possibility for a loader to show and go away when the content part is changing. This web application will need to be secure for users that register.

I've searched the web to investigate both frameworks, but can not seem to find the right answer so I can continue with my development

I do not mind creating separate REST services in later development if some other platform needs to hook up to the service if I decide to go with Thymeleaf.What do you guys think in what direction should I go, Thymeleaf or Angular? Any help and/or discussion would be much appreciated.

I am sorry if this seems like a general question, but I just need some basic guidelines to start with. Cheers!