Hello all. Thank you for helping me out.
Definitely there are some good suggestions to try. This can be confusing for somebody new to darkroom wizardry.
Thomas, I find your idea interesting. I'll definitely try your method.
Thanks Michael. I start by exposing first segment for 5 sec, than I move light blocking sheet to the next segment and expose that segment for 5 sec. So the first segment is now exposed for 10 sec, than I move blocker to the next segment, expose it for 5 sec.So the first segment is now exposed for 15 sec and so on. At the end my last segment is exposed for 5 seconds and the firs one foe 30 seconds.