Audit site on Yii2 recommendations to increase speed

An audit of the site is required to improve the speed of the xn----8sbhdcvdsuecgshvq9a... The site is created on Yii2. Tests are poorly loaded, and visually noticeable. We will provide access to the server. You need to understand exactly what the problem is speed.
The cost is approximate, offer yours along with the terms.