I will help you to acquire Russian.
A native English speaker corrected me saying that 'to' is unnecessary here. Is it correct to say
"I will help you acquire Russian"
'Mostly in conversation or informal English, the to is often left out.'
One can help one acquire something
and one can help one to acquire something
. Both are OK but they are not equivalent. (In)formality has little or nothing to do with it.
Will I shed some (new?) light on the help-with-to-or-without-to issue if I remind you of the prepositional origins of the infinitive marker "to"?
Keeping in mind how the preposition "to" articulates the relation between the verb and the object of "to" (go to school, drive to town, bring to justice, etc.) will let you see the role of the "to" in a different light. You should sense the difference in the minimally different pairs below.
"Please help me move the piano." vs. "Please help me to move the piano."
"Please help me pass the test." vs. "Please help me to pass the test."
Make note of the "distance" between the noun and the verb "help" that the prepositional "to" introduces.