I went through exactly the same thing. I really struggled in the first few months, nevermind days/weeks.
I had panic attacks, didn’t sleep, didn’t eat.
He’s almost 11 months old now and all the hard work is starting to pay off. He can still be really hard work some days and we have seperation issues, but we will keep working at it as we can see the progress in other areas.
Now he is great fun to have around and is great company. He loves everyone and other dogs, he’s always so happy around them. And on another level, he has been a support for me at times when I’ve been struggling with my mental health. I think he can sense it a little bit and tends to lump himself on me and stay close for a bit.
If you want it long term, stick at it.