Please tell me, could cocaine replace concerta (ritalin) for a few days until i get my prescription renewed?

Not a good plan: First of all, nobody needs stimulant medication every day, and many physicians give people holidays from them - like weekends or when on vacation. Cocaine is of unknown purity, can be overly strong or not strong enough, contains potentially lethal cutting agents (like levamisole), is illegal, requires using dealers where you can suffer violence or arrest. Altogether, a bad plan. Wait for renewal.