I was thinking that Bertholdt must have trained with his Colossal Titan so I was wondering how he would get down, considering Marley did not have 3d maneuver gear.
Humans with titan abilities have some control over what parts of the body is turned into a titan and to what degree. This is shown in The first season when Eren only builds a single arm, some torso and a head to stop the cannon from hitting himself, Mikasa and Armin.
To some extent this ability can be extended to deconstruction of the parts at different rates. This can mean the colossal titan may only deconstruct the torso and then the legs to get back down on his feet. This will require practice but is certainly plausible.