really, truly, indeed
Mahal kita talaga.
I truly love you.
Really, truly. So much!
It's really like that.
Talagang ganyan ang buhay.
Life is really like that.
A similar Tagalog word is totoo.
There is also another, unrelated meaning for the Tagalog word talaga, pronounced differently. It is usually in conjugated form.
Nakatalaga sa tadhana.
Destined by fate. (Written in the stars.)
A similar-looking Tagalog word is dalaga.