Its easy actually. First, you can use the (who, what, where, when) method. For example:
who- My dad
what- is planting a tree
where- at the back of my house
when- in the evening/ when he came back from work
See? One sentence is complete!
Another way is by reading and seeing English movies. This would improve you're language.
Lastly, be creative. You have to think out of the box when it comes to essays. Let your imagination roam wildly. That should do the trick.
Remember to polish your grammar by speaking perfect English almost every day. That could help a lot.