Hello aspirant! For GATE preperation many lectures are available on youtube as well as on unacademy.

You can refer this :https://www.youtube.com/channel/UCJjC1hn78yZqTf0vdTC6wAQ

https://www.youtube.com/channel/UCA6yfpYhy5sWMjRGOT-OAIQ

These may help you. you can refer videos. 

You can find your guest lecture 

On" www.thegateacademy.com"

You may have to pay for the guest lecture videos .if you are not able to pay for it ,go with  UNACADEMY LEARNING APP which is available in play store.

Hello,

You can get the video lectures on youtube, The "UNACADEMY" channel will be very helpful in the preparation for your GATE examination. "UNACADEMY" application is also available on the google play store in which you can get video lectures for GATE preparation.

All the best 

Thank you, yoy may visit again