Hello,
there's not enough information for a specific answer.
I'll tell you some important medical history elements to decide treatment:
- prior antibiotic use (last 3-4 months)
- respiratory problems like chronic 
obstructive pulmonary disease, 
bronchiectasis etc
- allergies to antibiotics
- creatinine levels and body weight
- ongoing symptoms besides cough: Fever, sputum, 
shortness of breath etc
- sputum culture results (if any exists)
If 40% of your kidneys are functional then you should have an estimated glomerular filtration rate (eGFR) of 40-45 mL/min. This is sufficient for most antibiotics to be taken at their full doses, if needed.
Only one tablet per day of co-amoxiclav 625mg seems like undertreatment to me but I should have creatinine levels and your body weight to calculate your eGFR. I'm sure your 
nephrologist did that already. 
You have to know that 
basal pneumonia markings on the X-ray may take more time to resolve than you may think. It can take 1-2 months AFTER complete treatment. So if you're better, don't let the X-ray scare you.
If you'd like a more specific answer then please ask me again providing the aforementioned information.
Kind Regards!