Sorry that I don't have enough reputation to post images.
The main problem is that it tells me that I need to install a C compiler and reinstall gensim or the train will be slow, and in fact it is really slow.
I have installed mingw32, Visual Studio 2008, and have added the mingw32 environment variable to my path.
Any ideas on how to solve it?
Similar to user1151923, after adding MinGW\bin to my path variable and uninstalling\reinstalling gensim through pip, I still received the same warning message. I ran the following code to fix this problem (installed gensim from conda).
pip uninstall gensim 
conda install gensim
Gensim needs a C compiler?