I can’t find Avoir du mal in any of my references. What’s wrong with ´lutter fairé ?

Hi Judy, 

Here is the link to the Kwiziq lesson explaining the expression, 'avoir du mal à' which is well used in French.

https://progress.lawlessfrench.com/revision/grammar/how-to-say-to-struggle-to-do-with-something-using-avoir-du-mal-a-avec

The verb 'lutter' woudn't do here as it means 'to fight' and is used accordingly.

Hope this helps!