There are many such editions of individual plays Arden Shakespeare Cambridge Shakepeare etc have many notes But Brodie notes on particular plays are for beginners/school students and could be helpful for someone learning English And there are cartoon/comic book versions too ... Many websites also helpful - Google Shakespeare - try their books section - you might find what you need on-line

She would be a quıte old American singer with one great song!

It means That you must take it as a given thing (i.e. - the condition has been or will be met) or "Take it as read that ..." would be a more colloquial way of putting it so it means If you take it for granted that our company invests or will invest in hiring and training ... This would usually be followed by a question such as ... "Can you give us a reason to hire you?" or "Would you like to work for us?" (as explained very well above - they are telling you what they offer - what will you offer in return?