Palaute oli rakentavaa ja helppo ymmärtää.

• palaute = feedback; the subject of the sentence
• oli = was; past tense of olla (to be)
• rakentavaa = constructive
• ja = and
• helppo = easy
• ymmärtää = to understand

So the sentence is built from two descriptions of palaute:

• oli rakentavaa = was constructive
• oli helppo ymmärtää = was easy to understand

Finnish has no articles. There is no separate word for the or a/an.

So palaute can mean:

• feedback
• the feedback
• sometimes some feedback

The exact meaning depends on context.

Rakentavaa is the partitive singular form of rakentava.

Finnish often uses the partitive with predicate adjectives when describing the general quality of an abstract or mass-like noun. Palaute behaves a lot like English feedback: it is often treated as a general substance/content rather than as one sharply bounded object.

So:

• Palaute oli rakentavaa. = The feedback was constructive.

This is similar to patterns like:

• Ruoka on hyvää. = The food is good.
• Kahvi oli vahvaa. = The coffee was strong.

Yes. It comes from the verb rakentaa, which means to build.

So rakentava literally has the idea of something building or constructive. In this sentence, it means constructive in the same way as in English:

• rakentava palaute = constructive feedback

The idea is that the feedback helps improve something, instead of just criticizing.

Helppo ymmärtää is a very common Finnish pattern meaning easy to understand.

It consists of:

• helppo = easy
• ymmärtää = to understand

This is an adjective + infinitive structure. English uses easy to understand; Finnish uses helppo ymmärtää.

Other similar examples:

• vaikea selittää = difficult to explain
• mukava käyttää = pleasant to use
• helppo lukea = easy to read

Because these are actually two different grammatical patterns:

1. Palaute oli rakentavaa

   • here rakentavaa is a predicate adjective in the partitive

2. Palaute oli helppo ymmärtää

   • here helppo ymmärtää is an adjective + infinitive construction

So even though both parts describe palaute, they are not formed in exactly the same way. That is why you get:

• rakentavaa
• but helppo ymmärtää

not two identical-looking adjective forms.

Because it is the first infinitive of the verb ymmärtää.

This is the form you usually see in vocabulary lists, and it is the form used after adjectives like helppo and vaikea.

So:

• ymmärtää = to understand
• helppo ymmärtää = easy to understand

Finnish does not need a separate word for to here; the infinitive form itself carries that meaning.

It is singular.

Finnish palaute often works like English feedback: even if it contains many comments, it is still very natural to use the singular.

For example:

• Sain paljon palautetta. = I got a lot of feedback.

The plural palautteet is possible when you really want to talk about separate pieces, sets, or types of feedback.

Yes. In this pattern, the adjective can agree with the subject.

Compare:

• Ohje oli helppo ymmärtää. = The instruction was easy to understand.
• Ohjeet olivat helppoja ymmärtää. = The instructions were easy to understand.

So in your sentence, helppo is singular because palaute is singular.

Yes, it is natural and understandable.

A Finn could also say something like:

• Palaute oli rakentavaa ja helposti ymmärrettävää.

That version means almost the same thing, but it uses helposti ymmärrettävä (easily understandable) instead of helppo ymmärtää (easy to understand).

So the original sentence is fine; this is just a possible alternative style.