This is Level 8 of the New Tunnel.
In this level, since the ceiling is quite low, you can easily jump onto the ceiling if you use the Duplicator. This sometimes may help you, or bring you the unexpected, so please be careful.
If you use the Child, also look out for the ceiling. You can do a high jump and float, and try to land on a far platform. Repeat this a few times and you will pass this level.
You’ll need to jump fairly late to get past the ramp. If you’re using the Child, you’ll need to move left immediately after jumping to catch onto one of the ceiling tiles, and then make one more jump (unless you have very good timing and jump as late as possible, which will cause you to float directly into part 9).