Sexual difficulties

how come in some couples, the guy will have difficulties inserting his pen*s into the girls vagina, as in the pen*s can't really penetrate into the vagina at all? why is this so? and there are any ways to improve it?

When a hard pen*s cannot enter in the vagina usuallay the reason is a certain unwanted contracion of the vagina muscles. Or abundant lubiracion or other medical help may solve the problem. (some alcohol for the girl may also help).

Maybe the girl is a virgin, or a recently deflowered one. Those are tight just because they've never been... um... 'used' and hence need some stretching before the pen*s can go in without difficulties. Or maybe the girl is just 'shutting you out' - when she contracts those muscles, it's pretty damn hard to get in.