How can one get rid of the guttural sound similar to ghunnah when reciting the Basmalah?

Correcting errors in Quranic recitation is achieved by reciting to a skilled shaykh and receiving direct instruction from him, in compliance with Allah's saying: "So when We recite it, then follow its recitation." As for ghunnah (nasalization), it occurs with the emphasized mīm and nūn, and with the silent nūn and tanwīn before certain letters, and with the silent mīm, tanwīn, and silent nūn before the letter bā’.