ERPNext with Ubuntu 18.04.3 Server

Hello, should with manual work without problems?
Last Updated: October 22, 2019:

It looks easier for me and it is a newer tutorial.

Problem speedysense 01:

wget https://github.com/wkhtmltopdf/wkhtmltopdf/releases/download/
sudo tar -xf wkhtmltox-0.12.4_linux-generic-amd64.tar.xz -C /opt`

Change to:

wget https://github.com/wkhtmltopdf/wkhtmltopdf/releases/download/0.12.4/wkhtmltox-0.12.4_linux-generic-amd64.tar.xz

Check:

wkhtmltopdf -V
wkhtmltopdf 0.12.4 (with patched qt)

save jannis

Now: Step 9 Install and Create Virtual Environment

Step 12 Get ERPNext Apps

Problem speedysense 02:

    bench get-app --branch master erpnext https://github.com/frappe/erpnext.git
INFO:bench.app:getting app erpnext
INFO:bench.utils:git clone https://github.com/frappe/erpnext.git --branch master --depth 1 --origin upstream
fatal: destination path 'erpnext' already exists and is not an empty directory.
Traceback (most recent call last):
  File "/usr/local/bin/bench", line 11, in <module>
    load_entry_point('bench', 'console_scripts', 'bench')()
  File "/home/jannis/erpnext/bench-repo/bench/cli.py", line 40, in cli
    bench_command()
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/jannis/erpnext/bench-repo/bench/commands/make.py", line 42, in get_app
    get_app(git_url, branch=branch, skip_assets=skip_assets)
  File "/home/jannis/erpnext/bench-repo/bench/app.py", line 125, in get_app
    cwd=os.path.join(bench_path, 'apps'))
  File "/home/jannis/erpnext/bench-repo/bench/utils.py", line 173, in exec_cmd
    raise CommandFailedError(cmd)
bench.utils.CommandFailedError: git clone https://github.com/frappe/erpnext.git --branch master --depth 1 --origin upstream

How can i solved this problem?

jannis