This is a kinda frecuent question

Check this answer from /u/Farahild

https://www.reddit.com/r/AskHistorians/comments/cyq8dz/how_far_back_in_english_history_would_i_be_able/

And this one from /u/ixnay2000

https://www.reddit.com/r/AskHistorians/comments/hlpqgc/how_far_back_in_time_could_i_a_modern_english/

Aaand this one from /u/Bayoris

https://www.reddit.com/r/AskHistorians/comments/8moelw/how_far_back_in_time_could_you_go_before_modern/