Zeminin pürüzlü yüzeyi kaymayı engelliyor ancak adım atmayı yavaşlatıyor.

The suffix -in is the genitive case marker indicating possession.
• zemin-in = “of the ground” or “ground’s.”
So zeminin pürüzlü yüzeyi literally means “the ground’s rough surface.”

In a genitive-possessive construction, the possessed noun must agree with its possessor by taking a third-person possessive suffix:
• zemin-in (genitive) yüzey-i (possessive) = “the ground’s surface.”

• kaymak = infinitive “to slip.”
• kayma = gerund or verbal noun “slipping.”
• kaymayı = gerund plus the accusative suffix -ı, because it’s a definite object of engellemek (“to prevent”).
Thus kaymayı engelliyor means “(it) is preventing slipping.”

It’s a buffer consonant. Since kayma ends in a vowel and we want to add the vowel-initial suffix -ı, Turkish inserts y to preserve phonological rules:
kayma + y + ı → kaymayı

1. adım atmak = “to take a step.”
2. Form the gerund: adım atma (“stepping”).
3. Add accusative -yı (definite object): adım atma+yı → adım atmayı.
   It’s the specific action being slowed down by yavaşlatmak.

The -iyor suffix can express:
• Ongoing actions (“is preventing,” “is slowing down”).
• General truths or characteristics (similar to English simple present).
Here it states a general property of the rough surface:
“It prevents slipping but slows down stepping.”

ancak = “however,” “but.”
You can also use:
• ama (colloquial)
• fakat (formal)
Example with ama:
Zeminin pürüzlü yüzeyi kaymayı engelliyor ama adım atmayı yavaşlatıyor.

Yes, but the meaning changes:
• zeminin pürüzlü yüzeyi (genitive-possessive) = “the ground’s rough surface.”
• zeminde pürüzlü yüzey (locative) = “a rough surface on the ground.”
Genitive shows ownership; locative shows location.

They’re causative formations:
• engel (noun “obstacle”) + -le- (make/do) + -mek = engellemek (“to cause an obstacle,” i.e. “to prevent”).
• yavaş (adj. “slow”) + -lat- (make) + -mak = yavaşlatmak (“to make slow,” i.e. “to slow down”).