Only resend the email

Go to the details of the sent campaign. In campaign statistics, click on the linke more details. You can copy the campaign or just the email. The new draft is then found under campaigns > drafts

Use the same target group again

With Create from campaigns target groups can be selected from sent campaigns. Go to target groups > Create from campaigns. You can choose the campaign and the email and decide between recipients, openers, clickers etc. Keep in mind that unsubscribes and hardbounces are automatically deleted from the target group.