The instructions feel unnecessarily convoluted to me when ChatGPT can do a very good job of doing the translations itself. I'd suggest you consider telling people to ask your app itself for help if stuck, and falling back to English if struggling to find words or if in need of translations.

Having tested your tool w/French, it in fact handles it perfectly well if I insert random English words in the sentences (and translates it into French), handles it fine if I ask it to explain words, and even if I ask it to repeat an explanation or sentence in English (hilariously, but I guess to be expected and provides nice continuity, it then spoke English with a French accent), so not much need to put things into Google Translate.

I sometimes do this with ChatGPT directly to practice language - just start asking it questions in another language and ask it to explain in English if something is unclear, or give it a short prompt to get it to correct my questions before answering.

The immersion you get when you can just start a sentence in the language you're practising and just switch "back" when you lack the vocabulary feels much better - you can be a lot more ambitious and throw yourself into sentences without a clue about how to finish them in the language you're practising.