Xin LU Lecture 1: Title: The slope of a fibred surface. Abstract: For a fibred surface it is known that the slope inequality proved by Xiao (and by Cornalba-Harris in the semi-sta ble case) is strict. It the arises a natural question to investigate the influence of some properties of the fibration on the behaviour of the s lope. In this talk I will talk about some recent joint work with Zuo on this problem. Lecture 2: Title: Geometry of an irregular surface of general type Abstract: Let S be a minimal surface of general type and of maximal Albanese dimension. The Severi inequality implies that $K_S^2\geq 4\chi(\omega_S)$. With the help of our new slope inequalities for non-hyperelliptic fibrations, we discovered the existence of an involution on such a surface with $K_S^2 < 9/2\chi(\omega_S)$. As a consequence, we obtained a characterization of the surfaces on the Severi line. This is a joint work with Zuo.