Improvements on essay

Personally speaking, I think the structure of the essay worked well. Before I wrote it, I list a structure of my essay so that I would be clear what I am going to write about. But the difficult part was to  state a thesis. I was not pretty sure how the thesis was like, and it is hard for me to think of one. However, after the help of the teacher,I figured it out. Yet I still need more practices. The weakness that I think my essay have is that it lacks details for my opinions of the painting. I talked about my opinions of the painting, but I didn't explain why I thought that way, after revising, I added some details follow the sentences.  Plus, when I tried to explain something, I found  that I cannot describe the thing that I want to express , which means I need to work hard on writing English.
If I could have more time on my essay, I would not only talked about my own opinions of the painting;I would do some research on the internet and find evidence to support my opinions and ideas. Plus, I would find a stronger thesis to support my essay and create more logical sentences to connect my thoughts together.