Not only Boomerang, but you could also create a GIF using the prebuilt gallery app of Samsung. Just keep in mind that this only works on Samsung Galaxy devices. Sideloading it onto other devices and trying might not lead to a satisfactory result.
Steps to Follow
To create a Boomerang, open any of the recorded video using Samsung’s default Galleryapp.
Next tap on Play Video. As soon as the video plays, you will see a GIFicon at the top right. Tap on it.
If you just want a GIF, simply hit Save, again situated at the top-right. However, to create a Boomerang, tap on 1.0x. Doing so will change it 2.0x. This will be your new video playback speed.
4. Now last step
Using the slider, you could also trim the video to the desired length.
Once done, tap on the Forwardarrow twice. This should add a back and forth effect to that video.
Thats it bro its so simple like if it is helpful to you.