gbr3: 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/gbr3 - from package: gambas3-runtime

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

Error in other languages:
gbr3: bevel nie gevind nie
gbr3: comandă negăsită
gbr3: comando não encontrado
gbr3: commande introuvable
gbr3: command not found
gbr3: käsku ei ole
gbr3: không tìm thấy lệnh
gbr3: komanda nerasta
gbr3: Kommando nicht gefunden.
gbr3: kommandot finns inte
gbr3: komut yok
gbr3: nie znaleziono polecenia
gbr3: níor aimsíodh an t-ordú
gbr3: no se encontró la orden
gbr3: no s'ha trobat l'ordre
gbr3: opdracht niet gevonden
gbr3: parancs nem található
gbr3: perintah tidak ditemukan
gbr3: príkaz nenájdený
gbr3: příkaz nenalezen
gbr3: команда не найдена
gbr3: командата не е открита
gbr3: 命令找不到
gbr3: コマンドが見つかりません