I got symfony/translation errors installing laravel 5 on remote server

Hello, Uploading my laravel 5 app on ubuntu under Digital Ocean server I got error in the browser:

Declaration of Symfony\Component\Translation\TranslatorInterface::setLocale($locale) must be compatible with Symfony\Contracts\Translation\LocaleAwareInterface::setLocale(string $locale)

Googling for decision I found that the error could need symfony/translation installation and I tried to install it locally on my kubuntu 18 and got error "

$ composer require symfony/translation                                     
Using version ^5.1 for symfony/translation
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Conclusion: don't install symfony/translation v5.1.2
    - Conclusion: don't install symfony/translation v5.1.1
    - Conclusion: don't install symfony/translation v5.1.0
    - Conclusion: don't install symfony/translation v5.1.0-RC2
    - Conclusion: don't install symfony/translation v5.1.0-RC1
    - Conclusion: don't install symfony/translation v5.1.0-BETA1
    - Conclusion: don't install symfony/translation 5.2.x-dev
    - symfony/translation 5.1.x-dev conflicts with symfony/http-kernel[v4.4.9].
    - symfony/translation 5.1.x-dev conflicts with symfony/http-kernel[v4.4.9].
    - Installation request for symfony/translation ^5.1 -> satisfiable by symfony/translation[5.1.x-dev, 5.2.x-dev, v5.1.0, v5.1.0-BETA1, v5.1.0-RC1, v5.1.0-RC2, v5.1.1, v5.1.2].
    - Installation request for symfony/http-kernel (locked at v4.4.9) -> satisfiable by symfony/http-kernel[v4.4.9].

My local composer.json :

{
    "name": "laravel/laravel",
    "type": "project",
    "description": "The Laravel Framework.",
    "keywords": [
        "framework",
        "laravel"
    ],
    "license": "MIT",
    "require": {
        "php": "^7.1.3",
        "arrilot/laravel-widgets": "^3.13",
        "doctrine/dbal": "^2.9",
        "fideloper/proxy": "^4.0",
        "laravel/framework": "5.7.*",
        "laravel/tinker": "^1.0",
        "mews/purifier": "^2.1",
        "phpoffice/phpspreadsheet": "^1.6",
        "proengsoft/laravel-jsvalidation": ">2.2.0",
        "s-ichikawa/laravel-sendgrid-driver": "^2.0",
        "spatie/browsershot": "^3.37",
        "spipu/html2pdf": "^5.2",
        "yajra/laravel-datatables-oracle": "~8.0"
    },
    "require-dev": {
        "beyondcode/laravel-dump-server": "^1.0",
        "filp/whoops": "^2.0",
        "fzaninotto/faker": "^1.4",
        "mockery/mockery": "^1.0",
        "nunomaduro/collision": "^2.0",
        "phpunit/phpunit": "^7.0"
    },
    "config": {
        "optimize-autoloader": true,
        "preferred-install": "dist",
        "sort-packages": true
    },
    "extra": {
        "laravel": {
            "dont-discover": []
        }
    },
    "autoload": {
        "psr-4": {
            "App\": "app/"
        },
        "classmap": [
            "database/seeds",
            "database/factories"
        ]
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\": "tests/"
        }
    },
    "minimum-stability": "dev",
    "prefer-stable": true,
    "scripts": {
        "post-autoload-dump": [
            "Illuminate\Foundation\ComposerScripts::postAutoloadDump",
            "@php artisan package:discover --ansi"
        ],
        "post-root-package-install": [
            "@php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "@php artisan key:generate --ansi"
        ]
    }
}

How this can be salved ? Thanks!