Depends how much you wish to hide and what system you are using
If somebody asks this question I assume they use Windows so I will tailor this response to Windows

If you only want to hide what you download or lolis you can use a USB drive and set the default downloads folder to it, and move anything you wish there.

If you want to hide your entire browser you can install a portable firefox or librewolf or whatever you use to that USB drive and run a separate browser from there. You can easily duplicate your configs and passwords and anything else onto it.

If you fear that your USB drive may be checked then consider encrypting it and the tool I used for Windows is Veracrypt. Veracrypt is mostly retardproof and it is graphical. You want to select encrypt a partition/drive and make a hidden volume. The rest is easy, follow whatever it says. Do not forget your password. If your parents check your devices in person then I do not believe they want to put much effort into it - so password cracking is not happening and you can set a short password. If you want to stay safe from the court it is harder but I can elaborate.
Once you made it and it is ready you select automatic mounting and put the password in when it is detected.
Do NOT write files into your USB before decrypting it as it may and probably will break its contents, only drop files once it is decrypted and only into the decrypted volume. Once you got a USB drive ready and encrypted try breaking it to figure out what you can and cannot do because there is no recovery unless you backup. If I am wrong anyone correct me.

That should cover pretty much anything.