Does anyone know about U-boat ranges?

[Stiebler]

Marhkimov said

I'm doing some research about u-boats ranges, but many websites have conflicting information.

It's always risky to use a tertiary source of information.
The primary source comprises the original data.
Books are written to summarise the primary sources. They may make mistakes, or they may copy each other's mistakes. They are the secondary sources.
Websites usually summarise the books, introducing their own errors, and often taking the most convenient single secondary source to hand. Only rarely will the website author actually have an authorative knowledge of the subject.

It's a little unnerving how many people on this forum refer to websites as their source of information when they quote "facts".

Try your local library for a book containing reliable information.