How is the relationship between the soldiers presented in the movie?

I actually think the movie does a pretty good job of
showing the relationship between the characters and staying true to the plot of the
novel by having Paul Baumer narrate the film like he narrates the
book.

Think about the opening scene where the soldiers are
lined up in a trench.  As the camera comes to a close up on each one, Paul is narrating
information about each character.  This not only serves as a brief introduction to each
character, but it provides necessary background information.  Additionally, it shows
that Paul knows his comrades and friends.  It also shows that he
knows each one equally, despite the fact that he went to school with some and others he
met in the war.

Also, if you review many of the scenes of
"downtime" when the characters are not actually fighting, you'll again be provided with
Paul's narration through flashbacks to school, flashbacks to boot camp and training, and
also present tense versions of conversations these men had with one another when the
stress of combat wasn't immediately present.  Even though the film is a little bit older
and the special effects do not mirror what is being done in film today, this is one
book-to-film adaptation that maintains much of the original plot and
tone portrayed by the author.  The relationship between Paul and the other
soldiers in the film are strikingly similar to his relationships with the same
characters in the book.