Performance, RAM improvement with partitions

I have a table like:

create table table_a
(
    id_a      mediumint unsigned   not null,
    id_b      tinyint unsigned     not null,
    id_c      char(10)             not null,
    value     tinyint unsigned     not null,
    TYPE      enum ('a', 'b', 'c') not null,
    DATE      date                 not null,
    constraint unique
        unique (id_b, id_c, id_a, TYPE, DATE),
    constraint fk_id_b_id_c
        foreign key (id_b, id_c) references table_b (id_b, id_c)
            on delete cascade,
    constraint id_a
        foreign key (id_a) references table_c (ID)
            on delete cascade
);

create index table_a_value_index
    on table_a (value);

create index table_a_new
    on table_a (id_b, id_c, DATE, id_a);

create index mks_date
    on table_a (DATE);

Now I would like to create partitions, but I am not sure how they will impact the RAM usage or the performance. I have tried the partitions like:

ALTER TABLE table_a
 PARTITION BY RANGE (to_days(date)) (
    PARTITION 2021_H1 VALUES LESS THAN (to_days('2021-07-01')),
    PARTITION 2021_H2 VALUES LESS THAN (to_days('2022-01-01')),
    PARTITION 2022_H1 VALUES LESS THAN (to_days('2022-07-01')),
    PARTITION current VALUES LESS THAN (MAXVALUE)
 ) ;

But that hadn't the expected RAM, performance improvement. My research has shown that smaller partitions could be better, but you should not have more than 50 partitions. If I would partition after each month, I could store the last 4 years (when max. 50 partitions are recommended), which would be enough. But how much would that impact my RAM usage and/or the performance? As far as I understood, the partitions are treated as separated tables, does that mean, that each partition will have their own indexes? The table has a size of 20GB+, but the indexes are 40GB+. It would be beneficial to reduce the loaded index size. The most used indexes are *unique* and *table_a_new*. The filter for *date* is a specific date or a range of 6 months. It is fine, that I will lose my foreign keys.