Hi! I played this (along with some other maps) in a netgame with a few other folks and wanted to give a few comments from the couple rounds I played of it.
For starters, I think 5 laps is too long. The races were over three minutes each, and while that's alright if it's due to 2-3 long laps, I think in this case your map kind of drags on with the lap count you have. A standard 3 laps would be fine, I think.
Also, your item boxes are way too frequent. I often couldn't even let the item roulette finish before I came up on the next set of boxes! I believe the rule Kart Krew has quoted is a set of boxes every 15-20 seconds if you're driving normally as Sonic on hard speed. I'm not sure if maps actually follow that very often, but you could definitely go down to just two or three sets of item boxes spaced somewhat-evenly throughout the track.
https://i.imgur.com/kAols07.png - This looks like missing textures?
https://i.imgur.com/NkTz0Qa.png - These fenced-off grass areas really suck to get knocked into by an item. You have to drive backwards in offroad all the way back onto the road to get back in the race. If you prefer it that way there's no need to change these, but in my opinion it'd be nice to put a hole in the far end of the fence that players can drive through and get back on the road without as much time loss. (It could also double as a small offroad shortcut for racers with sneaker boosts!)
You should consider re-encoding your music in a lower quality. It adds a lot to the WAD's filesize which makes it difficult to host on a server, since people often download WADs straight from the server instead of finding them here. The general standard for music in custom maps is a quality 0 OGG trimmed to the minimum possible length without cutting the music too short. (Trust me, it'll sound fine when the engine noises and sound effects are drowning it out.)
Overall though, I think it's a cute little simplistic course. If the frequency of item boxes was reduced and the music made smaller at least, I'd definitely call this a good map to have in a server's rotation.
