There is a profiler built into Emacs that will help:

https://www.gnu.org/software/emacs/manual/html_node/elisp/Pr...

https://www.emacswiki.org/emacs/EmacsNativeProfiler

Also, ESUP for profiling your startup time:

https://github.com/jschaf/esup

There's also a second profiler in Emacs, ELP, which can be used for testing individual functions:

https://www.emacswiki.org/emacs/EmacsLispProfiler