Hey =) These value studies look like a lot of fun, so I took the liberty and tried improving it with what I noticed. Though, I do have to preface it with a disclaimer: I have never done a value study before :D.
General things I noticed: Your value studies seem a bit dark overall and have quite a similar valuerange from fore- to background. Usually, the value range gets very narrow (little contrast), the further away something is from the viewer. I feel like there's to little of that in your studies.
I tried to remove the contrast in the background a bit and added more in the foreground, also trying to layer fore-/mid-/ and background in terms of value used. Note sure if this is accurate to your reference, but I felt like it's needed for the painting to read better.
Mayor key points I'd focus on are:
-your lightest lights/ darkests darks in the foreground should be more intense than in the background
- seperate objects a bit better where they overlap. I think it's okay to exaggerate the reference to make it read better (for example by adding atmosphere where it makes sense)
I hope this is of some use.