The advice of combining trading and at the same time investing can be misleading to the newbies coming in to this thread since you didn't make much clarification on this regard and knowing fully about the traits of a newbie in to Bitcoin investment. Every traders mindsets is that the price of Bitcoin should be going up and when it doesn't they become disappointed leading to emotions swings and unrest, and another thing about traders is that they don't easily use cold money unlike an investor because their focus is to maximize profits within short term which may or may not end up happening the way they expected. It is more pleasing to focus on investing than running the both trading and investing at the same time.
A trader can never increase or decrease the price of Bitcoin. The price of Bitcoin never fluctuates depending on just one person. When the demand in the market increases, the price of Bitcoin increases. When the demand for Bitcoin decreases in the market, the price of Bitcoin decreases a lot. The price of Bitcoin depends entirely on demand. But yes, in some cases, the price of Bitcoin increases or decreases depending on one person. For example, if there are big people like Donald Trump, owners of big companies, etc., they say good or bad things about Bitcoin, then it will be seen that the price of Bitcoin has increased a lot. Because all the people who follow them will be interested in buying Bitcoin. In this way, many big people have the power to fluctuate the price a little. But this does not happen for a long time, but for a very short time.