IR Remote with 4 buttons timer
Since you know the carrier frequency -36Khz and the receiver you will use -TSOP38236, then you should know that an IR remote control sends a "message" to the receiver.

The receiver uses the contents of the message to decide what should happen. While it is possible to use discrete logic for both the receiver and the remote (transmitter) it is FAR easier to use a micro controller to perform each of these processes.

As mentioned in "Comments" an Arduino is an example of a general purpose micro controller that can quite easily be setup (or programmed) for these purposes.

There are also pre-programmed transmitters and receivers that can be used as well.

Depending on your background in electronics and software you can decide which way would work best for you.

You can find examples of a "pre-built" type of product from as little as $15.00 to... well as much as you want to pay.

Aliexpress.com also has examples to look at.
Search for "4 channel ir remote", they have many to choose from.

If you are interested in using an Arduino and building a version for your self, search for tutorials on building an Arduino IR remote and receiver...

Since you have a receiver in mind, it is good for you to know that the common receiver frequencies are 36Khz, 38Khz and 40Khz. There are of course others, and you should also know that the 36Khz will receive the 38 and 40 just as well as it receives its own 36khz. 

In a former position I worked with IR remote transmitters and receivers for 12 years and know they are not very critical in the frequencies they work with.

There is a fair amount to know if you want to build one from scratch, the structure of the IR "data stream" and any pre or post amble information your receiver is looking for.

All certainly learn-able, but using existing hardware will be MUCH faster...