Developer PHP, Yii2, JS, MyS,L, C or Python

The project is written on PHP, Yii2, JS, MySL. It works, but not super fast, its a major problem. And the speed of processing and displaying data should be close to reality. So I thought about either partial or later (after tests) a full translation to something more lively - C or Python. Hence the requirements for special/team. That is, on the one hand, there must be knowledge of PHP, JS, to pick up current, on the other - additional specified languages for possible further optimization. I will be ready to listen to your opinion on the choice of the best technologies.