texstudio: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/texstudio - from package: texstudio

You may install the required package with command apt-get install {package}

Error in other languages:
texstudio: bevel nie gevind nie
texstudio: comandă negăsită
texstudio: comando não encontrado
texstudio: commande introuvable
texstudio: command not found
texstudio: käsku ei ole
texstudio: không tìm thấy lệnh
texstudio: komanda nerasta
texstudio: Kommando nicht gefunden.
texstudio: kommandot finns inte
texstudio: komut yok
texstudio: nie znaleziono polecenia
texstudio: níor aimsíodh an t-ordú
texstudio: no se encontró la orden
texstudio: no s'ha trobat l'ordre
texstudio: opdracht niet gevonden
texstudio: parancs nem található
texstudio: perintah tidak ditemukan
texstudio: príkaz nenájdený
texstudio: příkaz nenalezen
texstudio: команда не найдена
texstudio: командата не е открита
texstudio: 命令找不到
texstudio: コマンドが見つかりません