Learn Finnish: Minä olen kokenut paljon elämässä. - I have experienced a lot in life.

The perfect tense uses the present tense of olla (to be) as a helper verb, plus the past participle (the -nut or -nyt form) of the main verb. Here, olen (I am) is combined with kokenut (experienced) to mean "I have experienced".

What is the dictionary form of kokenut?

The dictionary form is kokea (to experience). It is a type 1 verb, so to make this past participle form, you take the strong stem (koke-) and add the ending -nut.

Could I leave out the word Minä in this sentence?

Yes, absolutely. Because the helper verb olen already clearly means "I have", you can just say Olen kokenut paljon elämässä. Dropping the "I" or "you" pronoun is very common in Finnish.

Why does elämä (life) become elämässä here?

To say "in" something, Finnish uses the inessive case, adding -ssa or -ssä to the word. Because elämä contains the front vowel ä, vowel harmony dictates we use the -ssä ending, making it elämässä (in life).