Translation:Open the door for me, I forgot my key.
А где " мой" ? I say it because literal translations are often required.
Sounds unnatural and might be incorrect. Generally speaking, when doing an action instead of someone else the action is done for that someone else.
"Open the door for me, I have forgotten the key" is not accepted. Americans use the preterite everywhere...
"I forgot the key" is more direct. I have no idea where this "my" is coming from.
Since crown levels whole Russian course is more like a course of anger management. The moderation team doesn't give a single ❤❤❤❤ about it. There are sometimes 16 out of 18 exercises wrong in one lesson. But it's not stopping them from asking for money.