Your child is behind in their speech development. They aren't hitting speech milestones, and they're falling behind their peers. You want to help. So let's talk about some ways to do this.
First, know that every child is different. While milestones give us an idea of how most kids develop, children develop at their own pace. Some kids just talk later than others, and that's OK. But some kids do have physical or psychological factors that delay speech. So make sure you have your child evaluated early by a specialist. That way you can rule out (or get treatment for) things like hearing impairment and other issues that might cause a delay.
Now, focus on using speech to interact with your child. Talk to them as much as possible. One way to do this is to narrate the different things you do each day. Talk them through the steps of everything you do as you do it. Describe what you're cooking. Talk to them as you're shopping. And respond to them when they communicate with you. If they ask questions, be sure to answer them. Read to your child. Sing to them. Find opportunities for social time with other children. All of these activities encourage language development.
Your child may also benefit from speech and language therapy. They may benefit from counseling. A specialist will give you advice about these options. They will create a plan that's right for your child.