Can't import the named export 'ApplicationRef' from non EcmaScript module (only default export is available)

Question

On adding any angular material in the app.module.ts, it's showing the above error. And the console errors are the following :

compiler.js:2175 Uncaught Error: Template parse errors: 'mat-toolbar' is not a known element:

1. If 'mat-toolbar' is an Angular component, then verify that it is part of this module.
2. If 'mat-toolbar' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.

angular version: angular version angular material version: 6.14.15 any help?