"我想吃鱼"and"我要吃鱼" have the same meaning. It means I want to eat fish.
And if the host what do you want to eat?You could answer "我想吃鱼"or"我要吃鱼".
"我喜欢吃鱼"means I love eating fish.
If you want to tell somebody you will have fish after a while,you could say "我要去(qu)吃鱼"
你好,我是婷婷(Trista)。我想说你一定能学好中文,因为如果你的头像是你自己的话,你长得很中国。
Hi , I'm Trista . I wish you could learn Chinese well , because you have a chinese face . I mean if the one in picture was yourself.