Postgresql – Is there a way to update 2 values each time calculating data on each row?

I have the following table:

CREATE TABLE IF NOT EXISTS import.dre
(
    idmov integer,
    companynumber integer,
    idproduct integer,
    dtdate date,
    nrtank integer,
    dailybalance numeric,
    startbalance numeric,
    endbalance numeric
)

Populated with the following query (10 first lines only):

INSERT INTO import.dre values 
(1, 104, 10, '30/09/2023', 5, 0, NULL, 7600),
(2, 104, 10, '01/10/2023', 5,-1089.42, NULL, NULL),
(3, 104, 10, '02/10/2023', 5,-404.62, NULL, NULL),
(4, 104, 10, '03/10/2023', 5,-470.57, NULL, NULL),
(5, 104, 10, '04/10/2023', 5,-604.97, NULL, NULL),
(6, 104, 10, '05/10/2023', 5,10381.23, NULL, NULL),
(7, 104, 10, '06/10/2023', 5,-593.54, NULL, NULL),
(8, 104, 10, '07/10/2023', 5,-713.27, NULL, NULL),
(9, 104, 10, '08/10/2023', 5,-995.01, NULL, NULL),
(10, 104, 10, '09/10/2023', 5,-736.25, NULL, NULL)

I have the task to update this table follwing this pattern:
1st: startbalance must be coalesce(endbalance,0) from the last day, grouped by companynumber, idproduct, nrtank. So, using those 10 lines, at day 01/10/2023 startbalance should be 7600 and so on.

2nd: endbalance must be the startbalance of the day plus dailybalance. So, at those 10 lines, at day 01/10/2023 end balance should be 7600 + (- 1089.42) and so on.

The Final result must look something like this (forgive me if that doesn’t look the most beautiful set of data you’ve seen today):

Select * from import.dre:

1, 104, 10, '30/09/2023', 5, 0, NULL, 7600
2, 104, 10, '01/10/2023', 5,-1089.42, 7600, 6510,58 -- 7600-1089.42
3, 104, 10, '02/10/2023', 5,-404.62, 6510,58, 6105,96 -- 6510.58-404.62
4, 104, 10, '03/10/2023', 5,-470.57, 6105.96, 5635,39
5, 104, 10, '04/10/2023', 5,-604.97, 5635,39, 5030,42
6, 104, 10, '05/10/2023', 5,10381.23, 5030,42, 15411,65
7, 104, 10, '06/10/2023', 5,-593.54, 15411,65, 14818,11
8, 104, 10, '07/10/2023', 5,-713.27, 14818,11, 14104,84
9, 104, 10, '08/10/2023', 5,-995.01, 14104,84, 13109,83
10, 104, 10, '09/10/2023', 5,-736.25, 13109,83, 12373,58

Is there some way to accomplish that? I’m trying (badly, I know) to use a for loop to update import.dre but I’m getting nowhere. If by any chance there’s a better way to do it than for loop, I appreciate. I don’t know how big import.dre can get.

I tried a lot of codes, but all of them updates the whole table (instead of calculating each row). The last function that i’ve created to debug is the following:

create or replace function teste()
returns void
language plpgsql
as
$$
declare
line record;
v_companynumber int;
v_idproduct int;
v_nrtank int;
v_dtdate date;
v_startbalance numeric;
v_endbalance numeric;
begin
for line in
    select 
        *
    from
        import.dre
    order by
        companynumber, idproduct, nrtank desc, dtdate 
    loop
        v_companynumber := line.companynumber;
        v_idproduct := line.idproduct;
        v_nrtank := line.nrtank;
        v_dtdate := line.dtdate;
        v_startbalance := lag(coalesce(line.endbalance,0), 1) over (
                partition by line.companynumber, line.idproduct, line.nrtank order by line.dtdate);
        v_endbalance := line.endbalance;
        update import.dre
            set startbalance = v_startbalance, endbalance = v_endbalance
        where
            companynumber = v_companynumber
            and idproduct = v_idproduct
            and nrtank = v_nrtank
            and dtdate = v_dtdate;
    end loop;
end;

This last query didn’t assign nothing at startbalance. Tried another ones, but there is a lot of querys to put here (the best one that I got put 7600 on each day at tank 5 after but I don’t remember how I got there)