500 Error with laravel when creating a new project

I try to learn laravel and after creating a project with.

i created a new project by typing "laravel new projectname" in cmd, installing composer and node.js, changed in cmd to the project directory and installed composer there and tryed to run "php artisan serve" comand. i got the message "Laravel development server started: http://127.0.0.1:8000"

when i open http://127.0.0.1:8000 i get a 500 Error (not from the browser. the error is from laravel).

I have absolutly no idea what could be wrong. I went by 3 guides for starters and they did not have this problem.

Is there anything i can do ti fix this error?

thank you very much in advance

edit: here is the logfile from storage/logs

[2019-10-12 20:13:12] production.ERROR: No application encryption key has been specified. {"exception":"[object] (RuntimeException(code: 0): No application encryption key has been specified. at C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Encryption\\EncryptionServiceProvider.php:44) [stacktrace] #0 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Support\\helpers.php(424): Illuminate\\Encryption\\EncryptionServiceProvider->Illuminate\\Encryption\\{closure}(NULL) #1 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Encryption\\EncryptionServiceProvider.php(48): tap(NULL, Object(Closure)) #2 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Encryption\\EncryptionServiceProvider.php(24): Illuminate\\Encryption\\EncryptionServiceProvider->key(Array) #3 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(800): Illuminate\\Encryption\\EncryptionServiceProvider->Illuminate\\Encryption\\{closure}(Object(Illuminate\\Foundation\\Application), Array) #4 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(682): Illuminate\\Container\\Container->build(Object(Closure)) #5 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(630): Illuminate\\Container\\Container->resolve('encrypter', Array) #6 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Foundation\\Application.php(768): Illuminate\\Container\\Container->make('encrypter', Array) #7 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(946): Illuminate\\Foundation\\Application->make('encrypter') #8 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(874): Illuminate\\Container\\Container->resolveClass(Object(ReflectionParameter)) #9 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(835): Illuminate\\Container\\Container->resolveDependencies(Array) #10 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(682): Illuminate\\Container\\Container->build('App\\\\Http\\\\Middle...') #11 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Container\\Container.php(630): Illuminate\\Container\\Container->resolve('App\\\\Http\\\\Middle...', Array) #12 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Foundation\\Application.php(768): Illuminate\\Container\\Container->make('App\\\\Http\\\\Middle...', Array) #13 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Foundation\\Http\\Kernel.php(215): Illuminate\\Foundation\\Application->make('App\\\\Http\\\\Middle...') #14 C:\\Users\\Rjinxil\\testproject\\vendor\\laravel\\framework\\src\\Illuminate\\Foundation\\Http\\Kernel.php(189): Illuminate\\Foundation\\Http\\Kernel->terminateMiddleware(Object(Illuminate\\Http\\Request), Object(Illuminate\\Http\\Response)) #15 C:\\Users\\Rjinxil\\testproject\\public\\index.php(60): Illuminate\\Foundation\\Http\\Kernel->terminate(Object(Illuminate\\Http\\Request), Object(Illuminate\\Http\\Response)) #16 C:\\Users\\Rjinxil\\testproject\\server.php(21): require_once('C:\\\\Users\\\\Rjinxi...') #17 {main} "}