someone gave me a older MacBook pro and I don't know how to reset and erase previous content

It's a pity you don't say what model of MacBook Pro this is. In general you should do the following.

Find out exactly which model of MacBook Pro you have got and which version of macOS is the latest version which it can run. There is a serial number on the bottom of the case which will help you to find this out.

Get a bootable macOS USB installer with the latest version of macOS for your MacBook Pro. These can be made by any Mac user, and are sold online as well.

Insert the USB installer into a USB port with the MacBook Pro turned off.

Turn on the Mac, wait for the sound, then hold down the Option/Alt key.

Select the option to install macOS using your cursor keys, then click on the arrow.

Wait for the next screen to appear, then select Disk Utility.

Select Show All Devices, then choose your hard drive/SSD from the top.

Select macOS Extended (Journaled), then click on Erase.

Quit Disk Utility.

Select Install macOS, then select your empty hard drive/SSD

The installation may go smoothly, or there could be some problems, such as not connecting to your network, and/or not recognising your Apple ID (if you have one). Select Skip to sort these problems out AFTER installation.

Enjoy your new/old MacBook Pro!

I think I have two pieces of good news for you! AFAIK here's one thing you can do with most MacBooks. Using Thunderbolt you attach an external display with a cable which is Thunderbolt on one end and whatever connector the external display uses. Unfortunately, there is a long running topic on here about external display issues under macOS Big Sur! I managed to use a MATSUI HDMI TV for several weeks, but that TV was old and has now broken down. If your built in display doesn't work or you can't read the part of the display you need, then you can try to force the display to appear on an external display as default. You can do this by closing the lid on your MacBook, then attaching an external USB mouse and USB keyboard. I think you may have to do this while the MacBook is turned on. By closing the lid you put the MacBook into sleep mode. You can then wake it up by pressing a key on the keyboard or a mouse button. If the lid is closed, then the MacBook will try to force the display to appear on the external TV or monitor and it should be displayed unless the TV or monitor isn't supported by your macOS version.

[Edited by Moderator]

If the old one boots, what model-year is it, and what version of MacOS is it running?