It is really difficult to give meaningful advice from 2D photos as it is hard to see where branches start and which direction they go. The photos do show a few things.
The reverse taper
@leatherback has already mentioned. Not too bad from one side but more obvious from some sides. I'd definitely get rid of at least one of those low branches. There is always a tendency to keep far more branches than necessary at the start.
Those branches are very low on the tree. One of the guidelines for bonsai style says that branches look far better when 1st branch is around 1/3 of total height. Guidelines are just that and you can ignore them and still make good bonsai but initially results do tend to look better when following some helpful guidelines.
You could remove both branches to make the first branch higher on the taller trunk or chop the trunk to have a shorter tree to match the low first branch.
The bulging top has also been pointed out. I agree that some of the top needs to go but I cannot see the branching well enough to pick where I would chop.
You mention that branches appear too fine. I guess that means branches are too thin for the thick trunk. That's because most of the branches are very young. This tree would have been grown tall then chopped down a couple of years ago in preparation for sale so most of those branches are only 1 or 2 years old. Some things just take time. The strong branches at the top are also hogging all the energy. That's normal but it does slow down growth of lower branches. We normally need to prune the top much more often and harder to allow lower branches to develop.
Roots: Check surface roots to see if they are higher on one side than the other. The lower trunk is currently planted vertical which puts the apex to one side. May look better and give other options if the trunk could be tilted one way or another but root placement will determine whether that can be done and in which direction.
Trunk taper: Bonsai look far better when the trunk starts thick and tapers gradually to the tip. Because this one has been grown fast and chopped high for immediate sale there is little taper in the trunk. For quality bonsai trunks are grown in a series of grow and chop cycles to get better bends and better taper. Not sure how long you want to spend on this project or what quality you are prepared to settle for. Real quality takes a number of years. many newer growers are prepared to settle for less perfect in order to get a quicker result. Lots of leaves in summer will hide a multitude of problems.
there are still lots of options for this tree but it is a waste of time setting out long term plans if you are thinking shorter term development and vice versa.