.... Be careful of using synonyms. If you are not very sure of their usage do not use them because they may give a very different impression if used inappropriately.
This is a major mistake lots of students do. Synonyms do not help always because in a language what is most important is the usage of words. For example, take the words "smile" and "laugh" They are close synonyms, but used to give different meanings. So, if you are not very sure, don't use synonyms. Instead write your sentences with known words.
In addition, the advertisements cannot manage their time well when they should inform adult products and when they should present children's goods only. In the night, this is the right time they could present adults' things.
Your sentences are pretty confusing. The above sentence is too long. Write short sentences with better clarity.