I agree with The Dark Lord, your map is almost ready
With the bridges, the bottom one is not curved enough in my opinion.
The top one just needs a few minor adjustments. The water above the bridge looks shadowy because the top row of the bridge is higher. You can make this not noticeable by making the water slope up slightly towards the bridge. The elevation on the top bridge needs minor tweaks with the brush size on smallest, to make it look smooth and nice. The top edge of the bridge looks kind of too low and bumpy. (not smooth and continuous)
The tile transitions can often be fixed by placing the tiles by hand, but in the worst case where you can't fix it you can use an object like a rock or tree to cover it (try to not make this too obvious though, don't put a big rock to cover every place, put dead trees and other stuff as well)
You should put the "underwater" part of the bridge supports (columns that hold it up in the water) If you look at the campaign maps you'll see they put the underwater part, the same as you do around hills when they connect to water. If you turn on "show flow direction" you should be able to find one which doesn't make your water flow the wrong way. (there are 3 tiles)
I like the way you put the supports close together, it looks interesting and different to other maps which usually have them spread out.