I used to train kickboxing 5 times a week twice a day

now a lot of shit happened I gained weight had a long break for a while and also the covid vaccine fucked me over a lil

I train 3 times a week now I weigh 89Kg

I used to weigh 78kg I'm 1,79cm tall about 5'10 I'm 22yo a male

So I've tried to come back but I'm slow as fuck even some beginners fuck me up while sparring and my stanima is just not there no matter how set my mind is my body just gives up

I tried training 3 times a week I got sick almost every month had a cold then a cold again now a knee injury

I trained today again my knee is ok about 78% so it was alright but I just noticed hoooow out of shape I am

what can I do about it any advice for people who try to be in their best form again? I just feel like a different guy now like I can't reach my old self I'm almost ashamed of myself.