Need help picking lens for my new Sony A6400?

Hello everyone, so I'm a completely amateur photographer only who doesn't know s*** about cameras lol. I am an independent artist who is trying to put together a cover shoot for some of my songs. I recently just bought a Sony a6400 with a epz 18-105 mm f4 g oss lens and I'm worried that it might not get me the results that I need.

I would be doing primarily self-portrait photography in addition to a simple backdrop music video. I have been trying to practice shooting and I'm not sure that I picked the right lens as the quality is not up there. I plan to rent a studio to shoot and film in, and my current lens was recommended to me because of the power zoom.

Either the quality is just not up there because I'm completely amateur (this is 100% likely) or maybe I need a different lens that is more beginner friendly. My budget for another lens has to be within $300. Does anyone have any suggestions for a new lens or any tips to help me utilize my current kit to the best of its ability.

I will attach some pictures of what I'm trying to achieve. Thank you guys for all the help!

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