Hello,

For Gate preparation you can use nptel for concept and make your basics clear. For numerical part you have to solve questions. You can get questions online or you can solve books which are also available.

For notes you have to mail to the concerned person or he might have given link in its description box.

You can watch his videos for complete understanding and tricks and tips for how to solve problems easily.

Apart from that there are many learning apps which will provide you materials for the preparation for GATE like unacademy,youtube, byjuys, edurev and many more.

In other words you have to read,understand and make notes by yourself. So just go for it and solve problems until you are completely not prepared.

Hope it helps!