The two lines on your chart represent the Bid and Ask prices.
The Bid price is the highest price buyers are currently willing to pay, and the Ask price is the lowest price sellers are currently willing to accept.
If you’d like a quick explanation, you can read more here: https://tradelocker.com/docs/what-are-bid-price-and-ask-price/
If you want to hide these lines, open Settings. On mobile, tap your account icon in the top-right. On desktop, open Settings from the bottom-left. Then go to Chart Panel and toggle the Bid/Ask price lines on or off.
You can also watch this short video on showing or hiding Bid/Ask lines: https://www.youtube.com/watch?v=DfHaMV0vKAU