Both of the sentences can make people understand, but the second one is a little weird, the first one is better. Besides, usually we say "从九月起", "从……（time）起" is a fixed pattern.

The first sentence is right if you rectify the phrase "从九月"（Chinese native speakers seldom use the expression”从九月“ which means ”from September“in English and I think what you wanted to express is "I began to learn Chinese in this college since September." so you can say "我从九月开始在这个大学学汉语” AND the second sentence just looks a little queer but you can make youself understood if you speak to a Chinese.

i think all right

从九月开始，我在这所大学学汉语。From September， I have began learn Chinese in this university.(right?)

what do you mean? if you want to say : I will ............... 从九月开始，我就要在这个大学学汉语了。 if you want to say: I have been .... 从九月开始，我就在这个大学学汉语了。