One question most people ask themselves when making happy birthday GIFs is whether they can add audio to their GIFs. Unfortunately, you cannot add sound or audio to a GIF file. What you can do is to animate the GIF and play audio from a separate file at the same time. An animated GIF has the .gif image or file format. This means that the file does not support any audio format. So if you wanted to say the words happy birthday in german on the happy birthday GIF, you will have to record your voice in a separate file and play it simultaneously with the GIF file.
In order to have video or audio in one file, the most effective option is to use a different file format like .mp4, .mkv, .webm or .ogg. Another point to understand is that the .gif format is very old. Its compression algorithm is not also perfect for images and videos. In fact, the reason .gif format is very common is that it is supported by web forums, social media networks and mobile applications that do not allow videos, but images only. A happy birthday gif is also preferred because it conveys a message in a simple manner.
However, it is also important to understand that there are certain workarounds on adding audio to such files depending on what is being worked on. In most cases, people who want to add audio to images usually discard the .gif file format and opt for .mpeg and .mp4 file formats. The images are then set to move in loops and then embedded into a webpage. But as noted above, the only workaround is to play an audio file simultaneously as the GIF with the words happy birthday in german. The process is however finicky especially when transferring the file to various social media sites with the audio attached.