Ago = There is time

Just when I thought that il y a was totally under control, came a twist.

Il y a un petit magasin en face de la gare. -- There is a small shop in front of the station.
Il y a beaucoup de magasins en face de la gare. -- There are many shops in front of the station.

So far so good; « il y a » could mean ‘there is’ or ‘there are’.
But …

Je suis venu ici il y a deux ans means, ‘I came here two years ago’.

Thus, « il y a » followed by time transforms the usage to ‘ago’.

This brings « il y a » into conflict with « depuis ».
« depuis » means ‘since’.

The following sentence is helpful ...

Je suis très occupé depuis je suis venu ici il y a deux ans. -- I am very busy since I came here two years ago.