My spleen is not functioning well. I had it diagnosed by a chinese
doctor, the spleen pulse was weak.  How can I improve my spleen
naturally. supplements etc. yoga exercises?

Did the doctor give any suggestions as to what to do?  Was he or she
even concerned about it?  I'm not sure what "the spleen pulse was
weak" means -- perhaps you should go back and discuss this more with
that doctor.

the spleen acts to filter out old blood cells; and it is part of the
immune system. Western medicine would say there is no way to evaluate
either of those functions except by certain blood tests. Some
alternative medicine approaches clearly have merit. Some do not. You
will need to decide for yourself if you wish to consider such an
evaluation as you describe meaningful. If so, the only answer will be
from a practitioner who believes in it also.