Hey @gabrieljim , It looks like you have some double verts. You can see it here 👇the vert on the upper left is not selected, but you can see the edge coming from there is orange and fading towards the next vert, this means there is a vert selected in that location.

Select everything with ‘A’ and press ‘M’ then select ‘By Distance’
As for selecting verts on the left side, you can turn it off with the ‘On Cage’ on the mirror mod.

Also make sure you have clipping enabled on the mirror mod.