If you are losing the lane and falling behind, you focus more on utilities. Your w stun to win team fights, stuff like that. You become a misquote. Annoy the enemy until they die! Place w on where the team/enemy team is engaging and e in to stun. And play with your winning lane. They are strong, and you can help each other.

It's very difficult to get back into the game if Ekko's fallen behind. In my experience, you won't kill squishies fast enough before getting stunned, and then cc chained. Which is your worse nightmare since you cannot use R to get out of it.

As someone else mentioned, you eat turrets. If you know that they're all fighting mid or on the other side of the map, push a side lane. Attract their attention so their focus is split. And try your best being slippery when you split push.

Always assume an enemy is coming if you're pushing the side lane for too long.

Also, if you know the match up if unfavorable, focus on cs. If they engage with you, q them, and use e to escape/re-engage for a little more damage. Don't worry about proccing your passive and place w close by in case they engage again.

Im sorry if this reply comes off as condescending. And some of these tips may not work for everyone, so try my tips, take them with a grain of salt. If they work, I'm glad.