No one would say "it helps to improving", but rather "it helps to improve". You are raising the subject of gerunds or infinitives as objects of verbs. Some verbs take one, some the other, some both. Thus "I look forward to hearing" is an example of a verb (phrasal verb) that takes a gerund as an object. There is no good rule about this subject. One can only memorize individual verbs.

You are correct. It should be: "this helps to improve."

I think the confusion is that the gerund ("ing") form of the verb is generally used after prepositions: I look forward to improving my fluency in that language. In your example ("it helps to improve") "to" is part of the infinitive form of the verb "to improve" and does not function as a preposition, so the "rule" that gerunds follow preposition does not apply. Many verbs are followed by infinitives, especially when they refer to future events: I want to read this book. He volunteered to help the needy. Take a look at this page which has many good examples: http://www.myenglishpages.com/site_php_files/grammar-lesson-gerund-infinitive.php