slow loading (Slow TTFB)

Hello everybody! I am new to website building and WordPress in particular. My site takes a very long time to load. Please tell me how I can solve this and what needs to be done for this.
https://www.webpagetest.org/result/201124_Di2P_63246af7a17554e2e5a4befe1b8c6d18/

This page has excessive amounts of unused JavaScript and css caused by autoptimize. Also consider combining your js and css files.