Against heimerdinger, Try to team fight in the open so he is unable to use his empowered E to stun your whole team. Do not fight inside the jungle as the size of his E is roughly the same as the jungle.
 
Once Heimerdinger hits level 6, he technically unlocks 3 new abilities. Be careful when trying to initiate a skirmish with him as he might just pull out his magic card and kill you.
 
Just like during the laning phase, you’ll want to destroy Heimerdingers Turrets Q as quickly as you can before a team fight is underway so he is unable to dish out tons of damage. Against heimerdinger, Try to fight as a team in the open air so that he is unable to use his E qualified to stun your entire team. Do not fight in the jungle because the size of his E is about the same as the jungle. Once Heimerdinger reaches level 6, he technically unlocks 3 new abilities. Be careful trying to initiate a skirmish with him because he could just remove his magic card and kill you.