Here you can find some websites that offer explanations and activities on the verb tenses in English:
https://www.perfect-english-grammar.com/present-simple-use.html
https://www.grammarly.com/blog/verb-tenses/
https://www.englishpage.com/verbpage/verbtenseintro.html
https://www.ego4u.com/en/cram-up/grammar/tenses
https://www.espressoenglish.net/english-verb-tenses/
Good luch!
