Learn Hardcore Turkish: Ben hafta sonu arkadaşlarımla parkta piknik yapıyorum. - I am having a picnic in the park with my friends on the weekend.

You can drop it. The ending -um in yapıyorum already shows first person singular. Ben is used for emphasis or contrast (e.g., “As for me…”). So both are fine:

Ben hafta sonu … yapıyorum. (emphatic)
Hafta sonu … yapıyorum. (neutral/natural)

Why does hafta sonu have no case ending? Should it be hafta sonunda?

Time expressions often appear without a suffix in Turkish. Hafta sonu works adverbially (“on/at the weekend”). Hafta sonunda (with locative -da/-de) is also possible and can sound a bit more specific, like “at the end of the week/that weekend.” Context decides. Both are correct here.

How do I say “this weekend,” “next weekend,” “last weekend,” or “on weekends (habitually)”?

This weekend: bu hafta sonu
Next weekend: gelecek hafta sonu
Last weekend: geçen hafta sonu
On weekends (habit): hafta sonları (often with simple present: Hafta sonları … yaparım.)

What exactly is inside arkadaşlarımla?

It’s a stack of suffixes: arkadaş-lar-ım-la

arkadaş = friend
-lar = plural (friends)
-ım = my (1st person possessor)
-la = with (contracted form of ile) So: “with my friends.”

Could I say arkadaşlarla instead of arkadaşlarımla?

You can, but the meaning shifts.

arkadaşlarımla = with my friends (your own group)
arkadaşlarla = with (the) friends (more generic/unspecified group)
In practice, when you mean your own friends, arkadaşlarımla is the default.

What’s the difference between ile and the suffix -la/-le?

They mean the same (“with”) and are interchangeable:

Separate: arkadaşlarım ile
Suffix: arkadaşlarımla
If the word ends in a vowel, add a buffer y in the suffix form: araba + y + la → arabayla (“with the car”).

Why is it parkta (with -ta) and not parkda?

The locative is -da/-de but it becomes -ta/-te after a voiceless consonant (p, ç, t, k, f, h, s, ş). Park ends in k (voiceless), so use -ta. Vowel harmony also applies: last vowel is a (back), so -ta not -te → parkta = “in/at the park.”

What’s the difference between parkta and parka?

parkta = at/in the park (locative)
parka = to the park (dative, direction)
Your sentence needs location for the activity, so parkta is correct. If you talk about going there, you’d use parka: parka gidiyorum (“I’m going to the park”).

Why piknik yapmak? Is there a single verb for “to picnic”?

Turkish often uses a light-verb compound with yapmak (“to do/make”) for activities: piknik yapmak = “to have/do a picnic.” Another common option is pikniğe gitmek (“to go for a picnic”). Both are natural, with a tiny nuance (doing the activity vs going for it).

Why isn’t it pikniği yapıyorum?

Because this is an indefinite activity (“having a picnic”), not a specific, previously mentioned picnic. Indefinite objects stay bare: piknik yapıyorum. A definite object takes accusative: pikniği. You’d only use that if a particular picnic is contextually defined: Dün planladığımız pikniği yarın yapıyoruz.

How is yapıyorum formed?

Stem yap- + progressive -(I)yor + -um (1st person sg):

After a/ı → -ıyor (yapıyorum)
After e/i → -iyor (geliyorum)
After o/u → -uyor (okuyorum)
After ö/ü → -üyor (yürüyorum)
Mini paradigm (yap-): yapıyorum, yapıyorsun, yapıyor, yapıyoruz, yapıyorsunuz, yapıyorlar.

Can -yor also express a planned/near-future meaning?

Yes. Bu hafta sonu piknik yapıyorum can mean a plan/arrangement (“I’m having a picnic this weekend”). For a more explicit future, use -ecek/-acak: Bu hafta sonu piknik yapacağım (“I will have a picnic,” intention/promise).

What if I mean a habit like “I picnic on weekends”?

Use the aorist/simple present: Her hafta sonu arkadaşlarımla parkta piknik yaparım.
The -r tense expresses habits/general truths, unlike -yor, which is ongoing or planned.

Can I change the word order?

Yes, Turkish is flexible, but the verb usually comes last, and the element right before the verb is emphasized. Your order (Time–Companion–Place–Activity–Verb) is very natural:

Hafta sonu arkadaşlarımla parkta piknik yapıyorum.
You could also say:
Hafta sonu parkta arkadaşlarımla piknik yapıyorum. (slight emphasis shift)

How do I make it negative or a yes–no question?

Negative: insert -ma/-me before -(I)yor → piknik yapmıyorum.
Yes–no question: add the question particle mi/ mı/ mu/ mü (separate word, with harmony):
- 1sg: Piknik yapıyor muyum?
- 2sg: Piknik yapıyor musun?
  Note: değil is not used to negate verbs, only nouns/adjectives.

Any quick pronunciation tips for this sentence?

ı (dotless i) in yapıyorum, arkadaşlarımla is a back, unrounded sound; don’t say “ee.”
ş in arkadaşlarımla is “sh.”
The progressive -yor carries stress: ya-pı-YOR-um.