It is necessary to optimize the loading time of the site

There is a site podarikvest.ru, which has very poor indicators for loading time. It is necessary to optimize. The analysis was carried out through developers.google.com/speed. It is necessary to achieve a minimum of 75 points for mobile and 90 for pc. For each additional point, in excess of those specified is ready to pay extra.
The site is self-written (php).
Optimization should be carried out according to the recommendations of Yandex and Google, as far as possible.
Full access to the site files will be granted.