Although this link is included on the page link Blackhorse gave you, this is also valuable resource How to find music & video. ie: use of filters when needed. And doing specific type searches. If using the advanced search option, don't fill in more than one category else you will get a lots of spam if not mostly spam in the search result.

Every search takes 3-5 minutes before the results have fully returned. So wait more than 5 mins after a search & right-click the search tab & choose Get/Find More Results.

For Porn, I think there are particular search terms that help. Depends on the movie you are after however.
For example if you did an Advanced search (from under the Options menu), you could search video type & adult category or R rating. However, this is not to say everyone puts such labeling on the videos they share. But should probably help to bring up some relevant results perhaps. Worth a try at least.

Beware of video spam below 3 MB in size. Some of them actually have viruses incorporated inside of them. As Blackhorse pointed out to look at that link, proper movies, even porn movies would be between 200 MB up to over 1 GB. But this also depends on the length of the video & the quality & dimensions.

AVI videos often do not show the video's dimensions or the length of the video. However, mpeg/mpg, mp4 / m4v will.

(AVI is an out-of-date video container for the newer video formats such as H264, unfortunately many people still use it. mp4 is far better. Not to say AVI movies are not good though.)