1.It’s suitable that a slim girl wears clothes in warm colors（改为同义句）
It’s （suitable ）（ for ） a slim girl（to ）（ wear ）clothes in warm colors .
2.It’s important for students to speak English well .（改为同义句）
（ It's ）（ important ）（ that ）students（ speak ）English well.
3.You’d better design your uniforms.（改为否定句）
You’d better （ not）（ design ）your uniforms .
4.Could you please tell me ...Does Tom like the English Comer （败为含宾语从句的复合句）
Could you please tell me （ if ） Tom ( likes ） the English Corner?