Car cranks but wont start, CEL & Battery lights on, no code.What now?

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I am not sure of which service exactly I am in need of. My car is a 2000 Ford Focus SE DOHC. Battery light would go on then off. Last time it was driven battery light stayed on. Then started to smell like eggs-opened hood and battery itself was steaming, battery acid leaking from battery. Towed home. Took off battery cables and they were melted. Had alternator, drive belt, and battery cables as well as a brand new battery replaced by a mechanic. He didn't correctly put the engine lift bracket (right next to the alternator) back. Not sure if this matters or will change the function of the car. after everything was replaced Now car will crank but wont start. Battery warning light, as well as check engine light is on now. Not able to pull any codes using personal code scanner. I need to get it fixed but I don't know what service I should get first when I go to mechanic. I don't want to spend a bunch of money for unnecessary things. Thank you