【1】have difficulty (in) doing sth.在做某事方面困难；ask sb. for help向某人寻求帮助，此句的句子结构为“if引导的条件状语从句+祈使句”，故答案为If you have difficulty solving these difficult problems, please ask me for help.

【2】There is /are sb. doing sth.有某人在做某事，in school uniforms作boys的定语，fly kites放风筝；on the playground在操场上。故答案为There are some boys in school uniforms flying kites on the playground. 

【3】help sb. do sth.帮助某人做某事；take a close look at近距离的观看；复合形容词two-hour修饰名词documentary，主语documentary是第三人称单数，一般现在时态要注意动词使用三单形式，故答案为This two-hour documentary helps people take a close look at the life of wild animals.  

【4】此句是unless引导的条件状语从句，主语用一般将来时态，unless引导的从句用一般现在时态，get lost迷路，故答案为Unless you have a map, you will get lost easily in the city. 

【5】此句是until引导的时间状语从句，根据句意判断，时态遵循“主将从现”的原则。not…until直到……才，advice为不可数名词，否定句中用any，故答案为I won't give you any advice until you tell me the truth.