Modification of the site on yii2

The website artonica.ru written in yii2, you need a php developer with knowledge of this angular framework.
The main problem that needs to be solved is the long loading of pages.
Here are some workarounds to resolve this issue:
But any other considerations about what should be done are welcome.

1) improve the site in the direction of lazy loading for images -
connect a ready-made library (this will make it possible to show the site
faster, and load the rest of the pictures as the page scrolls).
Now the preloader is shown until everything on the page loads.
Or just dont wait for everything to load to show whats already loaded.

2) make a separate video download in the admin panel for mobile
devices (video resolution will be less and accordingly they will be
load faster) and accordingly a script to change links to
video for the mobile version.



3) It is possible for the video to make an asynchronous download, that is, the videos will be
load in parallel with the loading of the site, which will also give faster to show
Page.

Promising tasks are the finalization of the feedback form and the addition of a hot button for new feedback functionality (not yet fully formalized).

The site requires technical support, so we are looking for a specialist for current tasks and for constant support in the future.