I deleted Whatsapp before my contact receives it with two ticks. He also deleted his Whatsapp but reinstalled it again. My question is, Will he still get my message? Because after reinstalling Whatsapp on my phone the message with just one tick was gone already. Thanks for your help.
When you send a WhatsApp message, as soon as it gets one check mark, there is no way to stop it from sending, unless you use the new Unsend WhatsApp message option, which you obviously didn't use because it wasn't available in 2014.
So as soon as there is one √ it is sent, even if you uninstall WhatsApp.
as soon as your friend reinstalls WhatsApp, he will get any messages that he hasn't received before uninstalling, and this includes any message that you sent with one ✓
In short the answer is yes, they will receive the message in question