Cto fired senior engineers and wants complicated frontend

Just landed a mid-level full-stack job in Bangalore through an agency that brings foreign companies here. But, plot twist - my CTO, who's abroad, axed the senior frontend devs and now wants me to handle some complex frontend stuff. To be honest, frontend isn't really my forte, and these overseas senior devs are super into code quality and reusability, not just churning out features. Feeling a bit in over my head and could really use some tips on how to up my frontend game, especially to meet those high standards. Any advice or resources would be awesome!