Learn Turkish: Şu çer çöpü hurca murca tıkıştırmak gereksiz. - Stuffing that junk into a storage bag or whatever is unnecessary.

The base word is hurç (a large storage bag). It takes the dative suffix -a because of the verb tıkıştırmak (to stuff into), causing consonant mutation that changes the ç to c (hurca). The m- reduplication then copies the entire inflected word, replacing the initial consonant with m (murca). The key rule is that both words in the pair must carry the exact same case suffix.

Is çer çöpü another example of m- reduplication?

No, this is a different kind of reduplication. Çer çöp is a fixed vocabulary pairing that means 'junk' or 'odds and ends'. Notice it takes the accusative suffix -ü at the very end (çöpü) because 'that junk' is the specific direct object being stuffed. Unlike m- reduplication, you don't add the case suffix to both halves of çer çöp.

What does the -ış- and -tır- part of tıkıştırmak add to the verb?

The root tıkmak already means 'to stuff' or 'to cram'. Adding the reciprocal/collective suffix -ış- followed by the causative -tır- creates tıkıştırmak, which emphasizes cramming multiple things together hastily or squeezing them into a tight space. It gives a much more chaotic, messy feeling than just tıkmak, which perfectly fits the action of shoving junk into a bag.