The development of free electron laser (FEL) sources, which provide extreme ultraviolet (XUV) and soft x-ray radiation of unprecedented coherence and almost transform-limited pulse structure, has opened up the realm of XUV/x-ray non‑linear optics. In particular, XUV four-wave-mixing (XFWM) experiments may allow, e.g., to probe correlations among low-energy excitations and core states, and to access the “mesoscopic” wavevector range (0.1-1 nm-1), inaccessible so far and fundamental to investigate nanostructures and disordered systems. Here we report on the latest advances and future developments of the TIMER setup at FERMI (Elettra, Italy) and of the test setup mini-TIMER (available at the DiProI end station), both specifically conceived for non-collinear XFWM experiments. In particular, we discuss the improvements on the beam transport of TIMER, that allowed the first all-XUV FWM experiments and the newly developed reflection scheme of mini-TIMER, that opened up the possibility of measuring opaque samples. Finally, TIMER and mini-TIMER are also suitable for time-resolved second order non-linear experiments, which are intrinsically surface sensitive due to symmetry restrictions, and hereby we discuss the foreseen extension to the XUV of interface specific probing of electronic processes, for example charge and energy transfer, with chemical specificity.