Verse 6: Whoever strives, strives only for his own sake. Indeed Allah has no need of the creatures. Allah (swt) does not need 
anything from us. He neither needs our struggles, nor our hard work. This means that whoever struggles, he does it for himself. The ulama and muffassireen have mentioned that this verse talks about Jihad al-Asghar (the Smaller Jihad) where the people take their weapons and fight the enemy.  
When we believe and then do good deeds, 3 things happen: The first thing is that Allah (swt) wipes away our bad deeds. The 
second thing is that we will be rewarded based on the best of what we did. Like sometimes when we go to the grocery store to buy fruits, we choose the best of what is available. Similarly we will all be rewarded based on the best of what we have done.
The third thing is that Allah (swt) will include us among the 
swaliheen  (to be explained in verse 9). We pray to Allah (swt) to grant us the correct understanding of the Holy Qur’an and help us to be amongst those who are good and also do good deeds. Ameen.