Source: Puzzle Page app
Look at the rightmost column in the part you haven't solved yet:
11 in four has got to be $1,2,3,5$ in some order. The top one must be $2$ or $4$, so now you know it must be $2$.
Then the $5$ in that column can only be in two places. Trying it in the upper possibility (just below the $2$) leads to a contradiction in the column to the left of that (two cells must be $1$ and $3$, we already have a $4$ above, so the remaining cell must be another $5$, contradiction). So the $5$ is placed, and then everything else should follow easily.