Edit: Thank you to everybody who helped. I got it back to English. I am currently learning Spanish but I’m only 80 days in on Duo so I was lost a bit there. 
Hello I was wondering if anyone could help me. My app switched itself to Spanish and I can’t figure out how to switch it back.
maybe try do it in the settings app???
click the link that says “alternatively click here”
also if you scroll to the very bottom of the home page, it should be there, click the language:
Looks like you’re not the only one to have that happen! I didn’t know it was a thing lol
Found it on the bottom of the explore page on the app. Good to know for future reference 
You can also try logging out and back in. It could be a glitch
That happened to me one time you have to go to your feed page then scroll all the way down to the bottom where it says the language and currency then change it to English and whatever currency
