oil paints can be tricky--depending on the outside humidity.
the simple answer is yes--linseed will thin your paints--it is the main vehicle of oil paints
add more & the paint-film thins.
moat oil paintings will be surface dry in about a month--
however the adhesion to the underlayer might not be dry for up to a yr.
if you want to speed up the drying time --add artists turpentine to your vehicle.
& if you really want to know the basics of oil painting read the "Artists' Handbook of Materials and Techniques " by
Ralph Meyer.
It can be a bit daunting;. but the man really tells the story.