Ola Miguel,
How are you?  Nice to hear from other u-boat modellers.
To create the splashguard on the upper edge of the tower,
I first glued small pieces of plastic that were spaced acc-
ordingly. Then a strip was wrapped and glued to this. The
edges were round off . Next  a small amount of putty was
added and filed to create the concave curve.
The doors on the tower are made from thin sheet of evergreen
plastic card and round rod was used to represent the hinges.
The Kreigsmarine flag is made from thin photocopy paper.
It was assembled using Photoshop, which allowed me to
create a reversed image, the two images were then folded
and glued with paper glue over some string . I rolled the flag
over a toothpick to create the waves.
The emblem of  U-96, the laughing swordfish,  is made
using Testor decal making paper and printed in an inkjet
printer. If you are modelling the same u-boat, I have some
spare decals that I can mail to you...just e-mail me your 
address.
I hope this helps answer your questions and enjoy  build-
ing this kit. It can be turned into a very nice model.
Have a nice day and happy modelling,  
 
 Joe