i really don't understand how the price increase or decrease?i saw that price coin changes randomly.If anyone help to know trading,I will be very grateful.
The most reliable way to predict the price is through witchcraft.
All kidding aside, if you're interested in learning TA, I would recommend you check out TheChartGuys on Youtube: https://www.youtube.com/channel/UCnqZ2hx679DqRi6khRUNw2g/videos. He uploads content daily, goes over the recent price action on a few coins (BTC, LTC, ETH, and one or another at times) in his crypto related videos, and often goes through some of the trades he made that day. Also, in his older videos, you can still find some more basic information like "What is an Inside Bar" (https://www.youtube.com/watch?v=GcFNRwu_Dm0), "How to Use Support and Resistance" (https://www.youtube.com/watch?v=d5RS_Mnpn2g), etc..