What mistakes do Native German speakers make when they speak in German?

Where to start?

Superlativeization of superlatives: the only, most optimal, most ideal word (instead of: the only, optimal, ideal word); In no way (Instead: In no way)
Words that don’t actually exist: Nevertheless (either nevertheless or nevertheless)
Incorrect or missing prepositions: at Christmas (instead of: at Christmas); In 2018 (instead of: in 2018); I go Aldi (instead: I go to Aldi)
The “Rhine-Based Form”: I am working (dran).

(Instead: I’m working right now.)

“Where” for relative rates: the money where the bank is located.

(Instead: The money that is in the bank. Now recognized in standard language.)

Dative instead of genitive: It was the car of Mr. Meier.

(Instead: It was Mr. Meier’s car.)

Wrong imperative: Eat your bread!

(Instead: Eat your bread!) Read the book!(Instead: Read the book!)

False indirect speech: He said he was on holiday.

(Instead: He said he was on vacation.)

False subjunctive II: She imagines herself a unicorn.

(Instead: She imagines she’s a unicorn.); It sounded like someone waslaughing.(Instead: It sounded like someone was laughing.)

Wrong Perfect Education: I hadthree days off last week.

(Instead: I had three days off last week.)

Incorrect bending of auxiliary verbs: The package has beenpicked up.

(Instead: The package has been picked up.)

The How-As-Mourning Game: Hanna is bigger than Paul.

(Instead: Hanna is taller than Paul.); It feels like you’re flying.(Instead: It feels like you’re flying.Or: It feels like you’re flying.);

False twists: To my knowledge, it’s Thursday.

(Instead: To my knowledge is Thursday.)

Confusion transitive and intransitive verbs: Grandma hung the laundry on a leash.

(Instead: Grandma hung the laundry on the leash.); Lena is terrified and becomes quite pale.(Instead: Lena is frightened and becomes quite pale.)

Incorrectly used plural: The doctor prescribed me an antibiotic.

(Instead: the doctor prescribed me an antibiotic;); She’s doing internshipsright now.(Instead: She’s doing an internship right now.)

False plural forms: The applications had different statuses.

(Instead: applications had different statuses.); There was something wrong with the pace.(Instead: Something was wrong with the tempi.)

Mistranslated Anglizisms: That doesn’t make sense.

(Instead: that doesn’t make sense.); At the end of the day, we will not sell anything with this strategy.(Instead: At the end of the day, we won’t sell anything with this strategy.)

Apparently instead of seemingly guessing: She apparently had a dog.

(Instead: She apparently had a dog. The “apparent” would mean she was pretending to have a dog.)

Everywhere “over”: He has already repaired more than fourteen cars.

(Instead: He has already repaired more than fourteen cars.)

The list could certainly be continued.