5.3) You must state the carbon environment (in this case it would be C=O
5.4) I believe for part a ur structure is right but your explanation isn’t specific enough, what does the chemical shift and splitting pattern indicate? - “The chemical shift indicates that the hydrogen is bonded to a carbon which is bonded to an ester bond and the splitting pattern indicates that there are 3 hydrogens adjacent to it” something along those lines, and the same for part b
I did OCR though, so the way they mark papers may very well be different so I would take this with a pinch of salt.