i, indeed, had to learn english grammar in order to learn spanish. When they taught us french as kids in school, it was just an exercise in memorization and I had ZERO conception that the various verb tenses actually mapped onto something in english!

This book (English Grammar for Students of Spanish) was useful to me. I assume there's ones for other target languages as well

https://archive.org/details/englishgrammarfo0000spin_q0j9_05...