Is it extremely hard to contract hiv ?

Rather easy : As easy or hard as having an unprotected sexual encounter or sharing needles with an HIV positive person. Good prevention makes it hard, life and ignoring the risk make it easy to get infected.

Yes and no: Depends on definition of "extremely hard". The average risk for any one sexual exposure is low. For example, if a woman has HIV, the chance her male partner will catch it averages once for every 2,500 episodes of unpotected vaginal sex. OTOH, most regular sex partners of infected persons eventually are infected. There is no transmission without sex or blood expossure, e.g. by shared needle