How do I get rid of this?

If you're trying to use the eraser and it doesn't work, then you must have converted your drawing to a symbol, or you're perhaps using an older version of animate and you drew it as objects. Try selecting the default selection tool (which you had selected in the screenshot), select any part of the drawing on the stage and hit CTRL + B. Then try to erase that part with the eraser. If you open the library panel and see that you got a symbol of your drawing, then that means that you converted the drawing to a symbol. If it's not a symbol, then you can turn off object drawing mode by selecting the brush tool, and clicking the button that looks like a circle in a square, towards the bottom of the toolbox.

However, there are faster ways of deleting things. You can click on any part of your drawing or drag a box around it to highlight it, as well as click on a keyframe (which is that rectangle with a dot on it) on your timeline, and it will select everything you have on the keyframe. Once you have something selected, you can just press Delete.

whenever i start drawing a round shape, the first curve looks like a straight line. help plz.

Can you give more details?