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Sounds like it might help to practice the chords individually. Doing the knee slap test, where you form the chord then put your hand on your knee then form the chord, rinse repeat. No strumming. Adding strumming will actually slow down the learning process in the brain.
Also try the “folded corners” method for placing you fingers, place the fingers in order 1-2-3, then 2-3-1, 3-1-2, 2-1-3, 3-2-1…..finally place them VERY SLOWLY all at once.
Another technique that works well for transitions is to do air transitions, very slowly move your fingers into position while in the air between the two chords. Really exaggerate the mention and go super slow.
Above all don’t get frustrated. It just takes time, but focused practice like described above can shorten the time.