The suggestion that a few coaching sessions would be helpful is a good piece of information.
Shadow strokes can really help your technique improve faster as well. If you know what an okay stroke looks like and practice shadow strokes in front of a mirror it really can help your stroke improve a lot faster. It would also be useful to have a good level player or a coach check if what you are practicing as a shadow stroke is actually good.
Shadow strokes won't solve all the problems of developing a good stroke because you don't have to adjust to the incoming ball. But they can help bypass the issue of "two different philosophies" that Lightzy correctly covered.
If you use shadow strokes to get decent mechanics into the muscle memory, you can learn to do a stroke where you use your body and your arm how you ultimately will want to.
In an "ideal" stroke the arm does bend at the elbow a certain amount. But it does not have to be a lot. Like your arm doesn't have to go from almost straight to very bent. And on smaller strokes the movement at the elbow joint can be small. But if your stroke is done with a relaxed arm movement, it will help the stroke and the elbow will bend, at least a little, during the stoke....just from having the arm relaxed.
This video has a little bit of okay information about the FH stroke: