I think it looks like a nice house, and I don't know your area but as you are getting viewings it can't be majorly out of step price wise. I'd focus on trying to improve on the feedback from those.
I'd focus on making the downstairs look as open and inviting as possible for viewers. Any clutter like the storage boxes in the kitchen should ideally be hidden. Space is key as it will make the rooms look bigger, oversized furniture/lots of visible boxes etc make everything seem smaller even if the room is actually pretty big.
I wouldn't do much to the garden if it's north facing, fairly small and overlooked, even if you have had comments about it. It will put some people off but there's nothing you can do about the main problems with it, so it's not worth focusing on. Just make sure it looks tidy and usable when people come to view. Some cheap flowers for colour could help with that but I wouldn't be spending lots on it.