Martina,
as I have commented earlier, dropping objects has a great link to objects rolling down ramps, and ramps has the advantage of slowing it all down so that children can really compare the effects of different masses, different materials etc and how gravity pulls them down.
If you use marbles or balls of similar size but different mass, the air resistance will be minimal, which will allow the role of gravity to come through more clearly.
This is a complex topic, and was not well understood for thousands of years, so children do need time to explore and develop their own understanding.
See Peeps (https://www.peepandthebigwideworld.com/en/educators/teaching-strategies/1/family-child-care-educators/2/learning-environments/17/ramps/) and and example in a class (https://wondersinkindergarten.blogspot.com/2015/04/ramps-and-pathways-play-based-learning.html)
all of which use the ideas from Iowa Regents Centre for Early Development Education. (https://qappd.com/wp-content/uploads/2021/07/fun_physical_science.pdf)