You have 20 minutes for task 1, so try spending 5 minutes on each paragraph. This might help you to organise your time better.
First 5 minutes
Read the question, make sure you understand the chart, highlight key information, then write your introduction by paraphrasing the question.
Second 5 minutes
Look at the chart and try to find 2 general points. Don't look at specific details; look for "the big picture". Write 2 sentences summarising the information.
Final 10 minutes
Describe specific details. Try to break this part into 2 paragraphs because it looks better. You could spend 5 minutes on each paragraph. Aim to write 3 sentences for each paragraph.