Help the folks that respond to your post, by adding a little more information.
What internet provider are you using?
Whay make and model router/modem are you using?
It may not be the router/modem, but limitations on bandwidth from the provider.
Have you contacted their customer support and asked them, or searched on their web site faq? Often this yields either a response or faq that suggests fixes.
If you are using DSL that comes into your house via a regular phone line, you need a method of connecting to your computer. The modem/router does this for you.
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"I love it when a plan comes together." - Hannibal Smith