Rrerku

Hi¡ I'm workin with a diagram and I don't know how to do. I almost finished it but the last part is so difficult. Can you help me?
I want to my diagram looks like

And the code that I have is the next

begintikzpicture[edge from parent/.style=draw,-latex]
node Lindelöf [sibling distance=6cm]
child node Casi Lindelöf
child node Débilmente Lindelöf [sibling distance=1.5cm]


;
endtikzpicture

From that I obtain the diagram of the image without the blue part. How can I conclude it? I really appreciate any help you can provide me.

One way is to add a node relative to the tree.

documentclass[tikz,border=3.14mm]standalone
usetikzlibrarytrees,positioning
begindocument
begintikzpicture[edge from parent/.style=draw,-latex]
node (Lin) Lindel"of [sibling distance=6cm]
child node Casi Lindel"of
child node D'ebilmente Lindel"of [sibling distance=1.5cm]


;
node[left=of Lin-1-1] (text) text;
draw[-latex] (Lin) -- (text);
draw[-latex] (text) -- (Lin-1-1);
endtikzpicture
enddocument

Or with draw[-latex] (Lin.south west) -- (text);

I would also like to draw your attention to the forest package.

documentclassarticle
usepackage[edges]forest
begindocument
beginforest
for tree=edge=-latex,calign=last,l+=5mm,s+=5mm
 [Lindel"of 
 [text,tier=murmel,alias=l]
 [Casi Lindel"of
 [D'ebilmente Lindel"of,tier=murmel,alias=b]
 ]
 ]
draw[-latex] (l) -- (b);
endforest
enddocument

Pure TikZ solution

documentclass[tikz]standalone
usepackage[utf8]inputenc
usetikzlibrarypositioning
begindocument
begintikzpicture
node (lind) Lindelöf;
node[below=of lind] (casi) Casi Lindelöf;
node[below=of casi] (debi) Débilmente Lindelöf;
node[left=of debi] (text) Text;
draw[-latex] (lind) edge (casi) edge (text);
draw[latex-] (debi) edge (casi) edge (text);
endtikzpicture
enddocument

Not knowing if it is good, but TikZ-cd may be an option: I prefer its syntax

documentclassstandalone
usepackage[utf8]inputenc
usepackagetikz-cd
usepackageamsmath
begindocument
begintikzcd
& textLindelöfarrow[ldd]arrow[d]\
& textCasi Lindelöfarrow[d]\
textTextarrow[r] & textDébilmente Lindelöf
endtikzcd
enddocument

matrix solution

documentclass[tikz]standalone
usepackage[utf8]inputenc
usetikzlibrarymatrix
begindocument
begintikzpicture
matrix[matrix of nodes,row sep=1cm,column sep=1cm] (x) %
& Lindelöf\
& Casi Lindelöf\
Text & Débilmente Lindelöf\;
draw[-latex] (x-1-2) edge (x-2-2) edge (x-3-1);
draw[latex-] (x-3-2) edge (x-3-1) edge (x-2-2);
endtikzpicture
enddocument