basic İ.Melih Gokcek solutions :)

Sadly there is nothing I can do except guide you how to :)

I would suggest playing with the teraforming tool mod in game :) that way it is possible to make a sunken thing yourself :) It is a bit tricky at first. But you can get the hang of it.
1: Dig a hole with the level decreasing tool 3-4 click will do.
2: Place the 2 highway lanes that you want sunken in the hole.
3: Use the level to level too with selected the normal height of the land around the highway and use it on the sides of the highway to make the hole tight and nice :)
4: Place 2 6 lanes or whatever road you want on the very edge of the slope terrain facing the side of the highway on both sides (perpendicular). If you see the trough the terrain a lot under the road it is too close. You should be able make the slope even steeper.
5: If you haven't made the highway ramps to the highway that is not sunken. You could have done that at any time you wanted it is not a big deal. :D

6: This is the tricky part. Use the highway ramps and place them on the side of highway on the slope. It should not change the terrain. But instead have pillars under. That way It will look better :) Draw the ramps just to the start of the normal level highway and then you should connect it smoothly without increasing the width of all the roads together. After you get it right and no terrain has been changed. Repeat 3 more times and connect to the highway.
7: Change the way cars should travel on the ramps if it is needed so you don't break your traffic a bit.
8: Bulldoze the rest of the city.

Voala You have a sunken highway thingy just like mine :3 ( DO NOT BULLDOZE YOUR CITY :D :D )

is there anyway to make these work since the update??

Otimo desenho !

And thank you as well sir :3

Beautiful! Thank you! Great modder!