If you have managed to download 800 files in two weeks, you are well on your way to being an expert simply through experience. To answer your questions:

you are given information about the quality of the other hosts through the star rating system, the declared speed of the connections (although not everyone tells the truth about that), and the bit rate. In theory, a four star, T3 host with a high bit rate file will download very quickly. Sadly, it doesn't always work that way. So, trial and error with each attempted download. If you are getting a poor response within the first minute of connection, cut your losses and go to another host.

There is nothing in your preferences box that will help. You should always set your searches for the widest spread of hits and then keep trying on everything you see that is interesting.

None of the information available through the advanced section of the statistics section will help you in the day-to-day business of finding files. It is a profile of the Gnutella network as a whole and only of interest if you want to start understanding some of the technical aspects of the magic of peer-to-peer file exchange.

There is no technical advantage in buying the Pro version. This is a shareware system and the money goes to pay the expenses of the few good hearted people who are working on Limeware. Whether you decide to pay depends on your conscience in taking the benefit of Limeware without giving something back to the developers.

And finally — keep saying to yourself, I am not a dummy, I am a successful downloader and I will get better through practice. There is an unwritten code about offering detailed guides. Basically, you have to join the club through your own efforts.

Good luck.