How many Hair Transplant sessions will you need?
Definitely depends on your level of hair loss and availability of donor hair.
For an advancing/advanced hair loss case, one might need 2-3 surgery sessions. At first the surgeon should fix/reconstruct your hairline and frontal hair. Then, you can come back for a second session after one year to fix the crown.
For a simple hairline fixing, 1 session will be sufficient. Unless you continue losing your original hair in the future then you might need a second surgery to fill in the lost hair.