Speaking during Tawaf is boleh and does not invalidate it. Nabi (shallallahu alaihi wa sallam) said: 'Tawaf around the House is like shalat, except that Allah has permitted speaking in it. So whoever speaks in it, let him speak only good.' This hadith establishes that while talking is allowed, it should be purposeful and good speech rather than idle chatter.
The sunnah practice during Tawaf is to engage in dhikr (remembrance of Allah), doa (doa), istighfar (seeking forgiveness), and Al-Quran recitation. You may supplicate in any language — Arabic is not required for personal doa-doa. There are no specific mandatory doa-doa assigned to each circuit, despite what some printed Tawaf doa booklets may suggest. Those circuit-specific doa-doa are later compilations, not from Nabi's practice. The only Sunnah-specific doa is between the Yamani corner and the Hajar Aswad: 'Rabbana atina fi'd-dunya hasanah wa fi'l-akhirati hasanah wa qina adhab an-nar.'
Brief necessary conversation with companions — such as coordinating meeting points, checking on someone's well-being, or answering important questions — is fine. However, extended worldly discussions, arguments, gossiping, phone calls about business, and loud talking that disturbs others should be avoided. Use the precious time of Tawaf to connect with Allah through heartfelt doa.