I have a problem with paragraphs. Well, I want every sentence that starts a new chapter or sub-chapter to have a paragraph. I still know how to make a paragraph. It is enough to give a blank line. E.g. UML (Unified Modeling Language) sentence is a technological technology for modeling should have a paragraph, but not there. Maybe someone knows how to do it?
\ section {Application Modeling Technology}
\ subsection {UML language}
UML (Unified Modeling Language) is a technological technology for modeling. Modeling to the
process by which we design the application, the presented application ~ \ cite {uml}.
The creators who created the UML were G. Booch, I. Jacobson and J.Rumbaugh ~ \ cite {uml2}.
In UML we can create 13 diagrams. They are divided into 3 main groups. To the first graphic
group that represents a static application

\usepackage{identfirst}. (It is quite common not to indent after \section as you don't need it to identify the start of a paragraph there.). – Ulrike Fischer Jun 07 '21 at 10:26