Debris in oil

[HopelessMoonGazer]

Hi everyone. Brand new to the forum. I am a bit of a newbie to scoots but I am in love. I have a ton of questions for you all. I'll start by telling you what I have. I started with a 49cc peace sports and quickly moved up to a 150cc Longbo Adventure. I bought it used...2008 with 350 miles. Been having some odd issues here and there. So I have 3 probs/questions that are priority for me right now.
1. I just did an oil change and found pieces of something in the oil....not metal, not rubber or plastic...one piece looks molded or shaped like the corner of a square...could this be a gasket? Along with that, oil blowing back to the front from under the seat area. Already put on new gasket for valve cover.
2. all of a sudden, on acceleration from a dead stop, my scooter makes a "shoving" feeling....like maybe the belt slips and then catches.If it was a car, I would call it a hard shift. Ideas?
3. I understand a lot of the parts on these scoots are inferior, anyone recommend a site that sells higher quality parts? I would like to replace all the basics with better quality.
Thank you in advance!