The Tones Are Important, But Not Essencial

You should not worry too much if you can't get tones perfect. Context is way more important than tones.

For example, below is a text written in pinyin with no tone markers. You still can understand everything, can't you?

ni men hao. wo jiao dawei, wo shi mei guo ren. wo zhu zai shanghai, wo de nv peng you hen piao liang.