LISTEN UP EVERYONE
ich gehe schwimmen does NOT represent an intention "I am going to swim". Its not a future expression either. German does not work like English where yiu can have "to be going to + a verb" to express future/intentional actions.
Ich gehe schwimmen simply means Im going swimming. I am heading to the place where I can swim.
Its two separate verbs/actions.
The second verb ends in -en because its an infinitive like "To swim". Thats why you cant conjugate schwimmen as well and have Ich gehe schwimme, it doesnt make sense.
Youre performing the action of going, so gehe is conjugated. Ich gehe - where? - schwimmen - to swim.
Quite so. "I am going to swim" means something completely different from "Ich gehe schwimmen" The German "gehen" does NOT indicate the near future, or intention, but the action of going (or driving) to some place, (in this case a swimming-pool or a lake or whatever it is) and then doing the swimming over there.
I believe since you congregated gehe, you don't need to conjugate a verb following directly after it. From what I remember in Spanish if you had two verbs next to each other, you didn't conjugate the second verb.
This is just me taking a guess on the situation and learning Spanish.
I am going swimming is not correct English. I am going to swim is correct. Yes it could be an acceptable slang somewhere and yes most people will understand you but nevertheless it is not correct English. Two verbs both with ING cannot be used in this format right after one another.