Which Running shoes to buy?

hi ,im a female runner (around 40-50 km per week).I run 4 days a week (1 long run around 15-17km and the rest are around 8-10km) and on the other days i just walk(10k steps)

Ive been using the decathlon running shoes but have been experincing slight pain in the left knee for the past few days. im wondering if it could be the shoes …?(might Be the training load which I’m def trying to bring down )

also could anyone please suggest some shoes I could look into tht would be best suitable for this mileage and for marathon training in the long run?*mostly road running