Nested formula with IFBLANK and XLOOKUP

[justenough]

I have a task list table with start dates in E and end dates in F
Task names are in C
User also has the option of selecting a task name in G (taken from the tasks listed in C) if the task in C can be performed at the same time as the task listed in G
Dates are dependent on the dates in the row above, UNLESS there is a dependent task name in G
If there is a task name in G then I need to check this value against the values in C, then populate E with what's in the matching C row's E cell

So:
C: task name
D: number of days of task (irrelevant here)
E: start date for task
F: end date for task
G: optional parallel task name

Using row 6 as an example (populating E6 with start date), these are the conditions:
- check if F5 is blank, if it is then make E6 cell blank as well (do not proceed with anything else, leave E6 blank)
- if F5 is not blank then check if G6 is blank
- if G6 is blank then populate E6 with F5+1 work day (i.e. make E6 = one day after F5)
- if G6 is not blank then find the matching G6 value in the C column and then populate E6 with the same value as column E for the row that the matching value is found in C

My first couple tries I ended up with this for E6 which I know is wrong:
IF((AND(ISBLANK(F5),""),
(IF(ISBLANK(G6),(WORKDAY(F5,1,Holidays)),
(XLOOKUP(G6,C6:C50,E6:E50,"ERROR",0)))))

Pretty sure there are fundamental issues with it unrelated to the number of parentheses but I'm stumped. Any help is greatly appreciated.; not sure if the functions used are the best for this.

 

[justenough]

Sorry, I'm not sure how to edit my original post but need to update the conditions. Please use THIS instead of the original for query info

I have a task list table with start dates in E and end dates in F
Task names are in C
User also has the option of selecting a task name in G (taken from the tasks listed in C) if the task in C can be started at the same time as the task listed in G
Dates are dependent on the dates in the row above, UNLESS there is a dependent task name in G
If there is a task name in G then I need to check this value against the values in C, then populate E with what's in the matching C row's E cell

So:
C: task name
D: number of days of task (irrelevant here)
E: start date for task
F: end date for task
G: optional parallel task name

Using row 6 as an example (populating E6 with start date), these are the conditions:
- check if C6 is blank, if it is then make E6 cell blank as well (do not proceed with anything else, leave E6 blank)
- if C6 is not blank then check if G6 is blank
- if G6 is blank then populate E6 with F5+1 work day (i.e. make E6 = one day after F5)
- if G6 is not blank then find the matching G6 value in the C column and then populate E6 with the same value as column E for the row that the matching value is found in C

My first couple tries I ended up with this for E6 which I know is wrong:
IF((AND(ISBLANK(C6),""),
(IF(ISBLANK(G6),(WORKDAY(F5,1,Holidays)),
(XLOOKUP(G6,C6:C50,E6:E50,"ERROR",0)))))

Pretty sure there are fundamental issues with it unrelated to the number of parentheses but I'm stumped. Any help is greatly appreciated.; not sure if the functions used are the best for this.