CODE = {["394"] = "H", ["29"] = "e", ["44"] = "l", ["141"] = "N", ["6"] = "o"}
function replace(match)
    local ret = nil
    for i, v in pairs(CODE) do
        if i == match then
            ret = v
        end
    end
    return ret
end

function decrypt(s)
    return s:gsub("(%d+)%s?", replace):gsub("  ", " ")
end

print (decrypt("394 29 44 44   141 6"))