Prestahop native theme menu module

[numberonebuy]

Good Morning. I'm using prestashop 1.7.3. and my DB is about 400MB. My server is VPS 2 CPU, with 2 GB of memory. I used a theme from Laberthemes, and what happens is that the apache memory is always very high and even crashes the server. I still can not figure out if a theme 1.7.2. is fully compatible with 1.7.3.

The native theme is very light, but I'd rather use it if that solved the problem. however I would like to have an alternative vertical menu in the native theme, because I have many categories.

Someone recommends a free. I do not like the native menu of the categories by using the "+" to do the dropdown.

Thank you.