Questions & Answers about Tämä näyttelijä on hyvin lahjakas.
What does the suffix -kas do in the word lahjakas?
How do I know whether to use -kas or -käs when making these adjectives?
It depends on vowel harmony. Since the root word lahja contains the back vowel a, you must use the back vowel suffix -kas. If the root word only contained front or neutral vowels, you would use -käs, for example älykäs (intelligent) from äly (intellect).
Why is hyvin used here to mean very? Doesn't it mean well?
Yes, hyvin is the adverb form of hyvä (good), so it usually means well. However, in standard Finnish, it is also very commonly used as an intensifier meaning very before adjectives. You could also use tosi (more spoken) or erittäin (more formal) here without changing the meaning.
How is the word näyttelijä formed?
It is formed from the verb näytellä (to act or to play a part). The suffix -jä (or -ja) is added to the verb stem to create a noun for the person who does that action, exactly like the -or in the English word actor.