I did similar to @DentdeLion. A computation using {t, 0, .001*tfin} took a few seconds and brought me to MaxMemoryUsed[] of 434 Mb. I then upped it to .01*tfin.

In[690]:= AbsoluteTiming[
 uifwave = 
  NDSolveValue[{op == 0, dirc, ic, dic}, \[Eta][t, x, y], {t, 
    0, .01*tfin}, {x, y} \[Element] mesh]]

Out[690]= {65.8217, 
 InterpolatingFunction[{{0., 53.5719}, {0., 70.}, {0., 94.5}}, <>][t, 
  x, y]}

In[691]:= MaxMemoryUsed[]

Out[691]= 1084091256 

Extrapolating from that suggests the full computation really takes more memory than most Mathematica kernels will have available.

Thank Michael for your reply...i executed one cell at a time or evaluated the whole notebook but the same eror or nothing happening...at this point I think the problem is my computer...I hope that tomorrow turning it on the teacher's computer will work...i really hope.. thank you again