Not really. Taking a walk after meals helps digestion. Taking a walk after a meal helps digestion. Slight modifications needed.

You actually do need it. The funny thing about nouns in English is that if you don't nail them down, they float about in a very non-committal way. This is fine if you're speaking generally but for singular countable nouns you do need an article, possessive pronoun, number, etc to "mark" it... we call these "determiners". "Taking a walk after meal" is so vague that the sentence is broken. "Helps" is still the better choice, but if you want a synonym it should be "assists".

in English, we always need put a article in front of a noun. So i think we have to put the other article in front of the "meal" and the "digestion" if you don't put "your" in front of

I think there are not any problems with your conversion. I think "YOUR" in sentence 1 means only for you. I think anybody who read this sentence will first think about him(her)self. But the conversion is correct. Thanks.

Taking a walk after mealS helps THE digestion - yes you can as the other response says.