Getting frustrated with potty training

Have a now 8 month old boxer mix pup that was found on the side of the road about a month and a half ago. Foster home didn’t potty train him and we’ve had him for about a month now. It HAS improved, I will say; but it is still insanely frustrating. He knows potty is outside – but has absolutely 0 patience if we take a second too long. He will go to the door to signal outside, but if we don’t immediately get to him he will just go. Absolutely will refuse to hold it. Only time he will try to hold it is at night while we sleep or in the crate, but he still has accidents in the crate. He goes outside SO often, like we take him out constantly. I just need someone to tell me that it will get better.