Camilo
Start with the adjective: soft / gentle. soft is describing the state of something e.g. that fabric is soft, and gentle refers to the action of something (you can't say a fabric is gentle). How does this help?
Softly implies how it is effecting the thing, and gently refers to how it is being done to the thing i.e refers to the action.
He touched her gently - you imagine how he is touching her
He touched her softly - you imagine how she is being touched
the wind blew gently - you imagine the wind blowing
the wend blew softly - you imagine the wind blowing on your face (softly)
Another example - in washing machines/ dish washers - there is always a "Gentle Cycle' - it implies that in that setting, the machine does its job gently - they never say 'soft cycle'.
Just remember gentle/gently always refers to something BEING DONE.
Happy to help if you need it.
Len
from Australia