How to show a link if the user is member of a specific OG group? I am not a coder but I'd like to do this line of code:

If the logged in user is a member of the Organic group team1
Then show a Link to node/add/team_1_content with 'Text' = create node
Else show nothing.
Create a block that includes that "Link to node/add/team_1_content with 'Text' = create node" as in your question.

Then use the Rules block visibility module. Here is a quote from its project page:


  The Rules block visibility module allows Rules components to be used to control block visibility. This provides Drupal administrators and developers extreme flexibility in controlling when blocks should be displayed on their websites, in addition to the default visibility options provided by Drupal.
  
  The general idea is that if you can do it with Rules, you can use it to control block visibility, so the possibilities are limitless:
  
  
  Need to show a block only for users registered more than a month ago?
  Perhaps you have a block that must be shown only between 8am-5pm on weekdays?
  What about displaying or hiding a block based on current weather conditions?
  
  
  All of this can be done by using Rules block visibility.


With that, and as per the "if you can do it with Rules, you can use it to control block visibility" above, you've reduced your question to making Rules "check if the logged in user is a member of the Organic group team1".

For an illustration of how to use this module, refer to my answer to "How to stop a Views block from displaying to admins, such as user/1?".