Saya rasa kucing itu sangat mesra.

Both mean to feel in an emotional or mental sense. The difference is formality:
• rasa – more colloquial, common in everyday speech
• berasa – slightly more formal or literary
Use Saya rasa… in casual contexts and Saya berasa… in formal writing or speech.

Malay typically omits the copula in present‐tense nominal/adjectival sentences. Instead of saying kucing itu adalah mesra, you simply say:
[Noun Phrase] + [Adjective]
So kucing itu sangat mesra directly means that cat is very friendly. Adding ialah or adalah sounds formal or stiff in everyday Malay.

Malay generally follows the Noun + Adjective order. In longer phrases with demonstratives and intensifiers, the structure is:
[Noun] + [Demonstrative] + [Intensifier] + [Adjective]
Hence kucing itu sangat mesra.

itu is a demonstrative pronoun meaning that. In Malay, demonstratives follow the noun:
• kucing ini = this cat
• kucing itu = that cat

Malay nouns are not inflected for number. To show plural, you use numbers or classifiers:
• dua ekor kucing = two cats
• sekumpulan kucing = a group of cats
Without context, kucing can be singular or plural; here, kucing itu implies a specific single cat.

sangat means very and precedes adjectives or adverbs. Alternatives include:
• amat (more formal/literary)
• benar (colloquial emphasis)
• sangatlah (adds extra emphasis)
Example: kucing itu amat mesra (that cat is very friendly in a formal tone).

Both mean friendly, but:
• ramah – everyday “friendly” or “welcoming.”
• mesra – suggests warmth or affectionate friendliness, common in formal or written contexts.
They’re largely interchangeable; choice depends on nuance and register.

saya is the polite first‐person pronoun in Malay. aku is informal, used among close friends or family. Using aku in formal settings can sound rude.
• Saya rasa… = polite/courteous
• Aku rasa… = casual/intimate (less appropriate with strangers)

Yes, Malay often omits the subject if the context is clear. However:
• Kucing itu sangat mesra is enough to state the fact.
• Rasa kucing itu sangat mesra feels like a headline or poetic style.
In everyday speech, you’d likely say Saya rasa kucing itu sangat mesra or simply Kucing itu sangat mesra.