This is pretty good, it's easy to see you really care about these people. I quoted a few things and made just a few suggestions in red:
Volunteers will be assigned
volunteers
are assigned
work not only for offering help and companionship
not only
to offertechniques of taking care of elderly in order
taking care of
the elderly in order
I think I have brought a little bright, help and emotional support to the residence in FCC.
i think you meant brightness to their day when you said a little bright, but it's not exactly clear what you mean
I often sit down and listen to their young stories
and listen
to stories of when they were young saying you listen to their young stories could convey that the stories are young (or new)
As a member of the community, we certainly will all get old,
as
members of the community, we
will all certainly get old
they surely have contributed a lot when they were young.
surely
had contributed