Adding an attachment
You can't add an attachment directly to your newsletter, but you can add a link to your attachment to the newsletter. For that, first upload your attachment to the cloud, for example to Dropbox or Onedrive. After that, get the link to your file and add it to your newsletter.
To add a link to your newsletter, select the word(s) in the text area of your template that you want to use to add the link (e.g. "Click here"). Then click on the link icon in the text toolbar, as shown below.
A new window appears, where you can copy the link URL. Click "OK".
Adding a video
You can add a video to your newsletter, by adding an image that links to the video.
For that, first make a screenshot of the video. You can add a "play" icon to the picture (use Photoshop, Gimp, Paint.net or some other image editing program for that). Play icons can be found for example from here.
Add your picture to the template as a usual. Then move your mouse to the upper left corner of the image, where a wrench icon appears and click on it.
The Image properties window will open. Copy the Youtube (or other video) link to the "URL" field and click "OK".
Adding a survey form
You can't add a survey form directly inside the newsletter, because most of the email clients do not support this, but you can create the form in web first and then add a link to it to your newsletter. If you already have a web survey form, move to step 2.
1. Creating a new Google Form survey
To create a new survey, go to docs.google.com/forms and click on the "+" sign that says "Start a new form".
A new window appears, where you can start adding questions. You can add questions by clicking on the "+" sign on the right of the page, and you can change the type of questions from the dropdown menu next to the question.
When the form is ready, click on the "Send" button in the top right corner of the page.
A new window appears with the send options. Choose the link option (1) and then copy the link address (2).
You can also view the Google Forms manual from here: Get started with Forms.
2. Adding the survey link to the newsletter
Open or create the template you wish to send out. Then add the link to your survey like any other link. To add the link to a word, select the word and then click on the link icon in the text toolbar. A new window opens, where you can paste the survey link and click "OK".
To add the survey link to a button, drag a button to the newsletter template and click on the settings icon of the button. Paste the link there.