It is difficult for me to explain this task. Hence, I have to teach it just by writing examples.

Let me try to explain: It can also be used to express a different situation or feature in the same time with another one. There are definite situations more than one. 

note: I will rearrange this explanation later. I don´t know, when I will do it but I will certainly do.

anne (mother), yemek (1meal, 2to eat), pişirmek (to cook (by fire)), yardım etmek (to help)

o+a(dative)---------------->ona (to him/her/it)

Annem yemek pişirdi. Ben de ona yardım ettim. (My mother cooked meal. And I helped her.)

We may get such a meaning: My mother cooked meal. I was there, too. But I didn´t cook, -differently- I helped her.

If it were in the meaning of "as well, too", the sentence would be in this order: Ona ben de yardım ettim. (I helped her, too.)

hediye (gift, present), vermek (to give), teşekkür etmek (to thank), küsmek (to take umbrage)

siz+e-------------->size (to you (2nd plural))

Onlar size hediye vermişti. Siz de onlara teşekkür etmemiştiniz. O yüzden size küstüler. (They gave you gifts. And you didn´t thank them. Therefore they took umbrage at you.)

Such a meaning: They gave you gifts. Normally, people thank them for a gift. And you -as differently- didn´t thank them.

If it were in the meaning of "as well, too", the sentence would be in this order: Onlara siz de teşekkür etmemiştiniz. (You didn´t thank them, too.)

aramak (1to look for, 2to call, to give a ring), akşam (evening), uyku (sleep), sabah (morning), iş (1work, 2job, 3business, 4something to do), erken (early), telefon (telephone), ev (house, home), unutmak (to forget)

-Beni akşam niye aramadın? (Why didn´t you call me last night?)

-Uykum vardı. Sabah da işim erken. Telefonu da evde unutmuşum. (I was sleepy. And my job is early in the morning. And I have forgetten the telephone at home.)

"Telefonu da evde unutmuşum" can and may also mean "I also have forgetten the phone at home.) Don´t be afraid. What you mean can be understood according to other sentences´ condition. Furthermore, the meaning of "too, as well" would be much clearer in the word order "Evde telefonu da unutmuşum." because "telefonu da" would come in front of the predicate. No complicated situation.

Rusça (Russian language), bayağı (quite, in a high/good quantity), öğrenmek (to learn), şimdi (now), Türkçe (Turkish language), başlamak (to start, to begin),

Rusçayı bayağı biliyorum. Şimdi de Türkçe öğrenmeye başlayacağım. (I can speak Russian much. And now, I´ll start to learn Turkish. (direct: I know the Russian in a good quantity. And additionally now, I started to learn Turkish))

For the meaning of "too, as well" : Şimdi Türkçe de öğrenmeye başlayacağım. / Şimdi Türkçe öğrenmeye de başlayacağım. (Now I´ll start to learn Turkish too.)

That´s all for now. I write new examples as long as I remember.