Sorry, didn't get that you want to disable Search (App). I wouldn't recommend to disable it as it's a part of operating system, like search function in previous versions of Windows. If you want, you can disable it, but take precautions. Run command as Admin :
Dism.exe /online /disable-feature /featurename="SearchEngine-Client-Package"
Agree, before you start tweaking DEFINITELY backup first, and at minimium create a system restore point. Even when using tools to do the tweaks, such as Softorrbits Privacy Protector I would still do this.Heres the one you could try =>Get Blackbird - Windows privacy, security and performance , but like i has been saying, its never ever too much saying again, BACKUP/RECOVERY/SYSTEM RESTORE before!