You need to give more information.
Some application types (e.g. Category) do not show a "New Topic" by default. Others do and then it is a lot more complicated to remove.
Also are you aware that the options that show can vary depending on the User Permissions you have set. It can be a good idea to create two users for your own forum, one to use as your administrator and the other that you can add and remove groups from so you can test how various forum features will appear to others.
Often it is a good idea to post the URL of your forum as then others can better assess what you see and what you are trying to do.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.