Order of Scenes and Sequels
Should I write a sequel at the end of the current scene or use it to start the next scene?
If you're just beginning, it's best to get into the habit of writing scenes and sequels as separate entities. Write a scene, then leave a scene break and write the sequel.
Even better, write the scene with a strong "failure" at the end that makes readers eager to learn what happens next. Then move into a new scene that deals with a different character in a subplot. THEN, when that scene ends, go to the sequel for your previous scene. This creates tension as readers wait to see how the character responds to the failure.
Having said that, separate sequels aren't strictly necessary, but they provide the "reaction" in action/reaction at the scene level, and they allow your characters to process their failures. But many authors experiment with the pattern.
If the pace of your novel is too slow, you may need to omit some sequels and write a couple of action scenes back to back to pick up the pace.
The sequel should never be long, and you may choose to include the character response directly after the scene action, without a scene break. That can work well, as long as it does not slow the pacing too much.
Initially, however, it is good to get in the habit of developing both scene and sequel separately, to make sure each one works well on its own. This swift action/response pattern is effective in creating a good pace that keeps readers reading.