How can I insert two row to supplier table?

CREATE TABLE supplier (
    supplier_nr NUMBER(10),

    supplier_id VARCHAR2(20) NOT NULL,

    price   NUMBER(10) NOT NULL,

    CONSTRAINT supplier_supplier_nr_pk PRIMARY KEY(supplier_nr),
    CONSTRAINT supplier_supplier_id_fk FOREIGEN KEY(supplier_id)
        REFERENCES varugrupp(supplier_id)
);

Insert the rows with a unique supplier_nr for each row and an existing supplier_id.

Can you give me one example please!

INSERT INTO supplier VALUES (1, 'ID', 10)

The values shown above depend on what is already in your tables, so you may need to change those. For example 'ID' needs to be in the varugrupp table.