Unable to do basic tezos-client commands in Carthagenet

Question

I'm very new to Tezos and would like to experiment a bit with its Smart Contracts. Due to some changes from Alphanet to Carthagenet some of the tutorials online are partially deprecated and I'm not sure if my proceeding is actually correct. (Mostly the ones on medium.com, which seem to be quite good, but still use Alphanet. Here and here). I'd be also quite thankful for a Tutorial that works straight away with the testing networks.

Please have a little patience if I mix some things up. Especially if the Sandbox, Alphanet and Carthagenet have equivalent functions.

I want to start with the very basics and run the command in the tezos-shell:

tezos-client get balance for my_account

But I'm getting the error:

Error:
  Unrecognized command.
  Did you mean one of the following?
    get ledger high watermark for <account-alias-or-ledger-uri> [--no-legacy-instructions]
    get ledger high water mark for <account-alias-or-ledger-uri> [--no-legacy-instructions]
    get ledger authorized path for <account-alias-or-ledger-uri>
[...]

I have downloaded the Carthagenet-Script:

wget -O carthagenet.sh https://gitlab.com/tezos/tezos/raw/latest-release/scripts/tezos-docker-manager.sh

And let it run: ./carthagenet.sh start Everything pulls and creates as supposed to, I see all the required Dockers.

./carthagenet.sh shell

Gets me into the shell, but I can't do anything useful.

With the sandbox and the Tutorial on the website most commands work, so I tried to use the tezos-client.sh on the node_1-Docker on the open port:

6ee8e77e99de        tezos/tezos:v7.0                  "/usr/local/bin/entr…"   About a minute ago   Up About a minute               8732/tcp, 0.0.0.0:19732->19732/tcp                                         carthagenet_node_1

But I can't make much sense from the error:

$ ./tezos-client -A localhost -P 19732 bootstrapped
Warning:
  Failed to acquire the protocol version from the node
  Rpc request failed:
     - meth: GET
     - uri: http://localhost:19732/chains/main/blocks/head/protocols
     - error: Unable to connect to the node: "Failed to read response: Malformed response first line: �M�By���7hG��������3Н�v���'Kt6M[��M��������k��_Z��l2r�uXRu�=�ݎ���aל,TEZOS_ALPHANET_CARTHAGE_2019-11-28T13:02:13Z"

Error:
  Rpc request failed:
     - meth: GET
     - uri: http://localhost:19732/monitor/bootstrapped
     - error: Unable to connect to the node: "Failed to read response: Malformed response first line: �M�By���7hG��������3Н�v���'Kt6M[��M��������k��_Z��V`��:-43��9஬�Um���,TEZOS_ALPHANET_CARTHAGE_2019-11-28T13:02:13Z"

What puzzles me slightly is the fact I can't even properly clean the old configuration:

$ ./tezos-client config reset
Warning:
  Failed to acquire the protocol version from the node
  Rpc request failed:
     - meth: GET
     - uri: http://localhost:8732/chains/main/blocks/head/protocols
     - error: Unable to connect to the node: "Unix.Unix_error(Unix.ECONNREFUSED, "connect", "")"

With the Sandbox the first error persists, but generally I can work:

qohelet@qohelet1604:~/persistent/tezos$ ./tezos-client config reset
Warning:
  Failed to acquire the protocol version from the node
  Rpc request failed:
     - meth: GET
     - uri: http://localhost:8732/chains/main/blocks/head/protocols
     - error: Unable to connect to the node: "Unix.Unix_error(Unix.ECONNREFUSED, "connect", "")"

qohelet@qohelet1604:~/persistent/tezos$ ./tezos-client -A localhost -P 20000 bootstrapped
Warning:

   The node you are connecting to claims to be running in a
                    Tezos TEST SANDBOX.
      Do NOT use your fundraiser keys on this network.
  You should not see this message if you are not a developer.

Current head: BLGknvhAsqwH (timestamp: 2020-05-06T19:28:18-00:00, validation: 2020-05-06T19:28:20-00:00)
Bootstrapped.

What are the requirements to work with Carthagenet? And why are my attempts failing?