I feel like I need more reps!
Concentrate more on the tempo of each rep, proper form, and complete range of motion and each set will last longer
You need slow and steady if you are just beginning a weight regiment. The body needs to be condoned with the proper range of motion with proper form. If you lift fast, you risk improper form, resulting in muscular imbalances and injuries. later on, you can lift the weight (concentric part of the lift) fast, pause, then lower the weight slowly (eccentric part of the lift). The body builds more lean muscle in the eccentric part of a lift. Lifting fast is primarily for power, trying to get a certain amount of weight from one area to the next as fast as possible. Most people do not need to do power training ever. You can look cut and shredded with just strength training. Only hit the power training if you are in sports, some kind of functional related activity, or just feel like doing it. All depends on your goals