Translation:We will do everything so they do not pass.
"Perché" as because needs the indicative, "perché" as "so (that)" the subjunctive. Compare:
"Lavoro perché tu spendi tutti i soldi" - "I work because you spend all the money". The first part of the sentence is a consequence of the second part. It is definitely known that "you" spend the money.
"Lavoro perché tu spenda tutti i soldi" - "I work so that you (can) spend all the money". The second part of the sentence is a possible consequence of the first. "You" haven't spent the money yet and might never do so, but the possibility is there. It helps to think of perché as "per ché" - "for that" in this case.
I'm just about ready to give up on this language. I wanted to learn because of my Italian grandparents but it's getting too crazy. The spelling alone is driving me nuts with all the double consonances. I always double them when they should be single and vice versa. Not to mention the silent G's.
I recommend supplementing Duolingo with some other material if you are really struggling with it. I too was hitting wall after wall, but i had the opportunity to take an italian class at university and since then a lot of things have clicked for me. Even if you can't take a formal class, youtube videos can be a major help to understanding. Duolingo is no good at explaining nuances like the "silent g" as you call it (it actually isn't silent and is serving a function!)
Maybe this will help. Note that this site says that perche' is translated "so that" when followed by the subjunctive - as it is here... Also you might note that it is etymologically formed as you suspected from the two words "per" and "che" but now one! Hope this helps.
Perché in italian is like "para que" in spanish and confuses me so much! you can also say "affinché" and here is an example: Voglio fare qualcosa affinché possa rimare con te" you can also use perché here but it sometimes confused me. If you want in the beginning you can use "Affinché" to help you learn, that's what I did, but my family in italian was telling me I sounded like a poet haha.
Interesting. In your example sentence, the subject doesn't change in either clauses so couldn't you just use "per" + infinitive (per poter rimanere con te" or "per rimanere con te")? You wouldn't need the subjunctive construction since there was no subject change from the independent to dependent clause. Correct me if I'm wrong.
Apparently you didn't understand my question. Based on your example, I would assume you were using the "yo" form of "potere", which means in the independent and dependent clases, the subject remains the same - "yo". From what I have learned and taught in Spanish and have used in Italian everyday conversations, if the subject is the same in both clauses, there is no need to use the "conjunction + subjunjunctive" construction. Instead, you need only use the preposition plus infinitive ("per poter rimanere" or "per rimanere"). If there is a subject change, however, the subjunctive is required along with the conjunctions you mentioned in your original message. Thank you for replying anyway. Have a nice day.