First of all, there´s something odd about it. Something that we can´t quite pick what is.  

Don´t know if it´s the centered alignment from the headings or something.  Or perhaps is the fact (just a probability here) that you made a writing and then used a translator, then lost the initial piece of text?

Anyway, lets give it a stab. 

This teaching (without capital T), you are talking about teaching in general, however, it´s my thinking here. Anyway, run a search withing Google Books with the word keys “teaching units”.

This Teaching Unit will have XX activities, the first of them was split into three, because I realized the need of students to have a Google account - Gmail - and also learning how to use Google Drive, once being on the computer lab making use of paper to develop activities proposals would be something a little backward...

This is a run-on sentence! You better use more periods (pontos finais), commas etc.

This teaching unit is composed of “n” parts, with activities (could be “x” parts, “y” parts, pick your variable of choice) – (also “each part being some activities, perhaps it´s a good idea to specify wich activity is “computer activities/search activities/pratical activities?”

It´s not advisable that you say “I realized”, although you can, anyway it may leave your students with that feeling of being edgy about your insights and even your knowledge. It´s better to be assertive/positive here.

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This teaching unit is composed of “n” parts, each part being a practical activity. The first one, in its turn, is divided into/split into three sections, that was done having in mind the need (these days) of students of learning how to create and use a G-mail and Google Drive accounts.

Once inside the computer lab/laboratory, keep them using activities only on paper, not pratical ones would seem a bit weird/awkward/outdated. *They must do them on the computer as well.

**The searches and other activities using the translator, will be stored in/saved to Google Drive.

Afterwards, both the student and the teacher can access the document there, and the teacher will edit/proof read it/grade the student´s work.

*Could be left out. It´s up to you.

** It will do, without “thus” just the same. Without it, one avoids wordness, unnecessary information.