My advice for task 2 introductions is to write them very quickly. Just write 2 sentences: one to introduce the topic, and one to give a basic answer. Let's look at how to do this for a "problem and solution" question:
The number of plants and animals is declining. Describe some reasons for this problem and suggest some solutions.
Here's my introduction:
It is undeniable that wildlife habitats are being destroyed and whole species of plants and animals are disappearing. There are several causes of this alarming trend, but measures could certainly be taken to tackle the problem.
In the second sentence you don't need to give any causes or solutions; save your ideas for the main paragraphs.