In Pcb view select routing->DRC (Design Rules check) which will check the board and complain about any errors. Best bet is probably upload the sketch (the .fzz file, upload is 7th icon from the left in the reply menu) so we can look at it and make suggestions. I don’t know of a good tutorial (there probably are some though!) on pcb layout, it is mostly experience over time and getting more experienced folks to review your design . One best practice is to route traces either horizontal, vertical or at 45 degrees.
Making parts is complex (and unlikely to get less so.) First try is a google search of the form “fritzing part part_number” (where part number is the part number of what you want or a description.) That will find existing parts that people have posted. Note posted parts can have errors so you need to check them. If you only need a small number of parts the best bet is to post a request in the parts help topic of the forum. I will usually make parts for folks as it isn’t worth trying to learn parts making for only a small number of parts. If you want to learn to make Fritzing parts these two tutorials (which usually stop parts making in its tracks 
) apply to current Fritzing versions:
I lately learned there aren’t links to the videos in Old_Grey’s tutorial so you need to do a google search for the title and then they come up on YouTube.
Peter